根据短文内容，从题中所给的A、B、C、D四个选项中选出最佳答案。

     If you like to check your smartphone from time to time, you are not alone. In fact, using apps（应用程序）has now become part of everyday life.

Changba

      Changba, which has been described as "the best mobile karaoke for sound", allows you to sing along to over 2,000 songs. You can also share your KTV recordings with friends on social media sites such as Weibo, Wechat, Qzone, etc. The app allows users to create a photo show to go with their songs and comment on other people's songs. Changba can even filter the sound. For example, it can make cat noises sound like a beautiful chorus(合唱).

Moment Cam

     Moment Cam brings you some of the most useful features a camera app can have, such as adjusting the flash(调整闪光灯）,continuous shots, adjusting the timer, and choosing different sizes for photo-sharing sites. But what sets the app apart from all the others is the choice of simple mini-buttons that you hardly notice are there.

Carrot

     Carrot, a to-do list app, is a task manager with a personality, When you succeed in finishing your tasks, for example, Carrot praises you with a message such as "Way to go. Soon you'll be completing other people's to-do lists".But if you fail to perform your tasks, Carrot might say, "I'm angered at your behavior." And it may change its background from white to black to show how angry it is. So, if you need an extra push to finish your tasks, give Carrot a try.

    What are you going to do if you are in a burning building？How will you escape？Do you know how to save yourself？ Please read the following passage.
    Escaping a fire is a serious matter. Knowing what to do during a fire can save you life. It is important to know the ways you can use and show them to everyone in the family, such as stairways and fire escapes, but not lifts.
    From the lower floors of the buildings, we can use windows. We should learn the best way of leaving through windows with the least chance of serious injury.
    The second floor window is usually not very high from the ground. An average person, hanging by the finger-tips will have a drop of about six feet to the ground. It is about the height of an average man. Of course, it is safer to jump out in a right way than to stay in a burning building.
Windows are also useful when you are waiting for help. Be sure to keep the door closed, or smoke and fire may be drawn into the room. Keep your head low at the window to be sure you get fresh air rather than smoke that may leaked（渗）into the room.
On a second or third floor, a person can escape through a window that open onto a roof. Then from the roof drop to the ground. Dropping onto cement（水泥）might end in injury. Bushes（灌木丛）and grass can help to break a fall.

    The word “day” has two meanings. When we talk about the number of days in a year, we are using “day” to mean 24 hours. But when we talk about day and night, we are using “day” to mean the time between sunrise and sunset. Since the earth looks like a ball, the sun can shine on only half of it at a time. Always one half of the earth is having day and the other half night. A place is moved from day into night and from night into day over and over by the spinning(旋转) of the earth. At the equator(赤道) day and night are sometimes the same length. They are each twelve hours long. The sun rises at 6 in the morning and sets at 6 in the evening. For six months the North Pole is tilted(倾斜) toward the sun. In those months the Northern Hemisphere(半球) gets more hours of sunlight than the Southern Hemisphere. Days are longer than nights. South of the equator nights are longer than days. For the other six months the North Pole is tilted away from the sun. Then the Southern Hemisphere gets more sunlight. Days are longer than night. North of the equator nights are longer than days. Winter is the season of long nights. Summer is the season of long days.

  Turns out，you're not just what you eat—you're also where you eat．

  Researchers found out that people had double the number of calories(卡路里)when standing in a messy kitchen compared to when they stood in an orderly one．

    The researchers had 98 women spend to minutes in kitchens，under the guise of (以……为幌子)asking them to wait for someone．Half of the women stood in a messy kitchen，with piles of newspapers，dirty dishes and a ringing phone．The other half of the women waited in a clean kitchen．

    Both kitchens had bowls of biscuits and carrots．Each woman in the messy kitchen ate twice as many cookies compared to those in the clean kitchen．

    Why did this happen?

    “Being in a messy environment and feeling out of control is bad for diets，''Lenny Vartanian，one of the researchers，said．“It seems to lead people to think，‘Everything else is out of control,so why shouldn't I be?'''

    The study's size was small，but the findings prove something we know all too well：Stress(压力)is bad for you．Stress often causes people to overeat．Beyond weight gain，too much stress can also increase a person's heart rate，and lead to painful conditions like headaches．

    While there are many ways to manage stress．including listening to music and exercising，this study shows that there are easy and quick things you can do to find calm．The next time you don't want to tidy up the kitchen，remember that the exercise will help you a lot in so many ways．

    There will be a kind of new cars in the future．People will like this kind of small cars better than the big ones．The car is as small as a bike．But it can carry two people in it．Everybody can drive it easily，just like riding a bike．Even children and old people can drive them to schools or parks．

    If everyone drives such cars in the future，there will be less pollution in the air．There will be more space for all the cars in cities，and there will also be more space for people to walk in the streets．

    The little cars of the future will cost less money to buy and to drive．These little cars can go only 65kilometers an hour，so driving will be safer．The cars of the future will be fine for going around the city，but they will not be useful for a long trip．

    This kind of cars can save a lot of gas（汽油）．They will go450kilometers，and then they have to stop for more gas．They are nice cars，aren't they？

    Can we "design" a baby like we design a handbag? It may sound crazy, but a "designer baby" could be possible now. Of course, at the same time, there are both agreements and disagreements with it.

    The "designer baby" idea comes from the research that allows scientists to make changes to human DNA and genes (基因). Usually, it is done when the baby is still just an embryo (胚胎). By doing that, scientists hope that "designer babies" will less possibly be born with some certain serious illnesses.

    During the 21st century, the idea became so popular that the research developed very quickly. Now, it has been firstly used to help born babies with their illnesses. One example of this is that Dr. Adrian Thrasher of University College London was able to save a 1-year-old child from leukemia (白血病) with the help of it. People learned that it was not only illnesses they could change, but also a baby's gender and looks. A well-known event happened in 1996. An American couple, Monique and Scott Collins, decided to use this research to help them choose the gender of their next baby. They wanted to have a baby girl for they have had three sons. Moreover, people could also decide babies' eye color, hair color and even things like height or how sportive babies will be.

    Some people argue that it is not ethical (道德的)to design babies like designing a bag. It is strongly against the nature's rules. Besides, it may not have any bad influence on the baby now, yet no one knows what will happen to him and his children after many years.