We always think that it's OK for us to leave our plants home during our vacation as plants won't scream like pets, right?

    A recent study done by a group of scientists at the Tel Aviv University has discovered that some plants will scream when they are under stress.

    The research was carried out on tomato plants and tobacco plants by cutting their stems (茎) and depriving (剥夺) them of water. A microphone was placed 10cm away from them. When their stems were cut, the plants started "screaming" between 20 and 100 kilohertz, and the scientists guess that this scream is probably meant to warn other plants nearby.

    When the tomato plants' stems were cut, 25 ultrasonic (超声的) pain sounds were recorded in an hour, and at the same time, 15 ultrasonic pain sounds were recorded from the tobacco plants. When they were deprived of water, the tomato plants recorded even more pain sounds with 35 pain sounds in an hour while the tobacco plants recorded about 11 pain sounds.

    The plants also acted differently to different kinds of stresses. For example, the tobacco plants gave out a stronger "scream" when they were deprived of water than when their stems were cut. But plants that were in no immediate (立刻的) danger gave out less than one ultrasonic sound per hour.

    The group of scientists said that plants are not as quiet as we had always thought, but in fact their voices are so high-pitched that we just can't hear them.

    Last year, another study has found out that plants feel pain when they are touched or hurt and they will give off a terrible smell.

    We are lucky to live in a rich country where we have many things. However, most of us usually {#blank#}1{#/blank#} (waste) some things.

    Electricity is one thing that we waste most. Lights, TVs, {#blank#}2{#/blank#} (radio) and other things are often kept on even when no one is using them. We should turn them off {#blank#}3{#/blank#} we do not need them. It takes  {#blank#}4{#/blank#} (little) than a second to do it. Anyhow, not wasting electricity saves money, because we do not have to pay for the electricity we do not use. The {#blank#}5{#/blank#} (two) thing that we often waste is water. Fresh water is precious, so it shouldn't be wasted. It is only a simple matter of turning {#blank#}6{#/blank#}a tap. I am sure everybody can do this {#blank#}7{#/blank#} (easy) if he wants to. Another big waste is food. My mother used to cook so much food that much of it was thrown away. I told her we had wasted so much {#blank#}8{#/blank#} (food). She thought I was right and now cooks mainly what we can eat.

    It is not right to be wasteful. I find there is a simple way of not wasting things. That is {#blank#}9{#/blank#} (use) only what we need. Do not touch what we do not need. {#blank#}10{#/blank#}this way, we can stop being wasteful.

    Don't be too surprised if you see a car going down the road without a driver in Beijing these days. {#blank#}1{#/blank#}Last month, Baidu began to test its self-driving cars on open roads in Beijing.

    {#blank#}2{#/blank#}Since then, companies like Tesla, Uber and Baidu have been working to produce and test their own self—driving cars.

    Self-driving cars are safer than regular cars. {#blank#}3{#/blank#}They can remove the stress of driving and allow disabled or blind people to get around more easily.

    {#blank#}4{#/blank#}In one test, researchers pointed a laser pointer (激光棒) at the car's sensors (传感器) while it was moving. The car mistakenly thought that the laser beam was in its way and slowed down or changed the direction.

    The software that is used to direct the cars may not be safe enough. {#blank#}5{#/blank#}When we use our computers or smartphones, they sometimes crash (崩溃) without any reason. But if this happened to a self-driving car, the result could be deadly. Improvements to the software could be a solution to this problem.

    Have you ever considered starting a fitness program? Since exercise can reduce the risk of diseases, improve balance, help lose weight, better sleep habits and even make you confident, you should start a fitness program in the following steps.

    Test your fitness level

How many meters can you walk or run in one minute? How much time does it take you to swim 50 meters? What is your heart rate (心率)? The data (数据) of your fitness level can help you know what activities you need.

    Design your fitness program

You may have begun your daily exercise. But a personal plan helps more. First, you should have your fitness goals (目标). For example, what do you want to look like, to be slimmer or quicker? A balanced plan will help you start low, progress slowly, do right activities and even allow you to recover (康复) if you get hurt.

    Prepare things needed for sports

You need something practical, enjoyable and easy to use. It could be a pair of trainers, a volleyball or a bicycle. You can also download fitness apps (应用程序) on your mobile phone to measure distances, calories burned or your heart rate.

    Take action

Now you're ready for action. When you begin, don't always try tough tasks. Listen to your body and reduce exercise time if necessary.

    Monitor your progress

Test your fitness level again six weeks later. If you have achieved your goals, increase exercise time to continue improving.

Starting an exercise program is an important decision. By planning carefully and acting step by step, you can have good health.

阅读下列短文, 从下面每个小题的A、B、C、D四个选项中选出最佳选项。

A study conducted by the University of Leeds in the United Kingdom suggest that watching cute animals may lead to a reduction in stress and anxiety.

The study examined how watching images and videos of cute animals for 30 minutes affects blood pressure, heart rate(心率) and anxiety. In December 2019, 19 people, including 15 students, joined in the study.

"There were some kittens, there was puppies, there were baby gorillas, there were quokkas —cute creatures found in Western Australia, are often referred to as 'the world's most cheerful animals'." Dr. Andrea Utley, a professor at the University of Leeds told CNN. The study was timed during winter exams, a time when stress is at an especially high level for students, according to Utley.

 The study recorded that the average blood pressure dropped from 136/88 to 115/71, which the study pointed out is "within ideal blood pressure range." Average(平均的) heart rates were lowered to 67.4 bpm, a reduction of 6.5%. Anxiety rates also went down by 35%.

"I was quite pleasantly surprised that during the session, every single measure for every single participant dropped some — heart rate reduced, blood pressure reduced," Utley said. "When they left, they filled the questionnaire(调查问卷) in again and showed that they were feeling less worried."

When questioning the participants, the study found that most preferred video clips over still images, particularly of animals interacting with humans.