B

    Language students often think they have memory problems. They worry because they can't remember words. In fact, the problem usually isn't with their memory. The problem is with how they study.

    To remember words better, you need to understand how memory works. There are two kinds of memory: short-term and long-term. When you see, hear, or read something, it goes first into short-term memory. But short-term memory lasts for only a few seconds. You will only remember something longer if it goes into long-term memory. Your long-term memory is like a very big library with many, many books. And like a library, it's organized (有条理的). When you put away a book – or memory – you can't just leave it anywhere. You have to choose a place where you can find it again.

    How can you do this with vocabulary? The answer is to work with the word and think about the word in new ways. You can do this by writing new sentences that include it. Even better, you can invent a little story about the word, with people or places that you know. Another way is to make a picture in your mind with the word. For example, if the word is height, you can think of the tallest person you know and try to guess his or her height. All of these activities are good ways to think about words. They make the meaning of words stronger in your long-term memory. And they give a way to find a word when you need it.

    Every time when I look at the moon, I wish I could go there. Do you wish you could fly to the moon in a spaceship one day?

For hundreds of years, men have wanted to travel to the moon. When they looked at the moon, they asked many questions. Was the moon hot or cold? Were there any plants or other living things there? There were many, many other questions.

    We know much about the moon now. Scientists have studied the moon for many years and have found out many facts. So far, some men have got to the moon on spaceships.

    Scientists have found that the moon is much smaller than the earth. It is about one quarter the size of the earth. It is traveling round the earth all the time. There are not any plants or other living things on the moon, because there is no air or water there.

    Days and nights on the moon are very long. One day on the moon is as long as two weeks on the earth. One night is also as long as two weeks on the earth. In the day the moon is very hot. At night it is very cold. The moon is much hotter and much colder than the earth.

    There is another surprising thing. On the moon things are not as heavy as they are on the earth. Isn't that interesting? Perhaps one day we can all travel to the moon. It must be great fun.

    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.