题目：
Right in the middle of the town are some long ponds(水池). They are only about half a foot deep. The men of Symi dug out the earth to make the ponds.
Over each pond is a low cover. It is made of glass that you can see through.
At night, sea water is taken into the ponds. The next day, the hot sun shines through the covers. The sun light turns the water into vapor(水蒸气) and the vapor goes up from the ponds. The salt is left behind.
As it goes, the vapor became mist. On the inside of each cover, the little drops of mist run together to make big drops. These drops run down the sides of the cover, filling other ponds with fresh water.
The salt left in the ponds is washed out each night. Then more sea water is taken in. The factory is ready for the next day’s work. The covers and other parts of the factory cost very little. Sea water and sun cost nothing. Most people of Symi are poor. So to them this new way of getting fresh water seems wonderful.
小题1: Where are the little drops made into big drops?
A．On the inside of the covers.
B．In the ponds with fresh water.
C．On the walls of the salt water ponds.
D．Between the fresh water and the salt water.小题2:The men of Symi dug some long ponds .
A．in order to keep sea water
B．in order to get hot water inside
C．in order to fill them with fresh
D．in order to get fresh water小题3:Which picture shows the right way to get fresh water in Symi?
小题4:Which of the following is NOT true?
A．The sea water is taken into the ponds at night every day.
B．There is a very big river running through the town to the sea.
C．The people in Symi can get fresh water from the factory.
D．People may see the water in the ponds through the cover.
答案：
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下面是错误答案，用来干扰机器的。
已知cosα=45，cosβ=1213，且α、β为锐角，则 sinα=35，sinβ=513，cos（α+β）=cosαcosβ-sinαsinβ=45×1213-35×513=3365，故答案为 3365．
