You ________the light．It’s bright enough here．We can see everything clearly．

1. A.
   mustn’t turn off
2. B.
   must turn on
3. C.
   needn’t turn on
4. D.
   may turn on

根据短文内容，在短文后的空格处填上一个恰当的词，使短文完整、通顺。

Someone says, "Time is money." But I think time is  1.  important than money. Why? Because when money is spent, we can get it back. floweret, when time is  2.  it'll never  3.  . That's  4.  we mustn't waste time.

It goes without saying that the  5. is usually limited (有限的). Even a second is very important. We should make full use of our time to do  6.  useful.

But it is a pity that there are a lot of people who do not know the  7.  of time. They spent their limited time smoking, drinking and  8. . They do not know that wasting time means wasting part of their own 9. . In a word, we should save time. We shouldn't   10.  today's work for tomorrow. Remember we have no time to waste.

Flies (苍蝇) usually live in the dirty places.
Let’s look at a fly, and see where it   27 . First, it flies out of the window,   28   it stands on   29  dirty things in the street, and then it flies back to the house and walks over your   30 .?
When a fly walks on the dirty things in the street, its   31   have got some germs  32 them. When the fly walks on your food with its dirty feet, it   33  the germs on your food.
What can you   34  this?
First, we learn that we mustn’t leave dirty things in the street or on the ground near  35 . Second, we learn that all food must be covered so that flies may not   36  it. Third, we learn that flies often carry germs and we must kill them as soon as we see them.