光合作用的实质是（　　）

    Many people think that twins are exactly the same. But some of them are not! Al and Mike are twin brothers. They look the same and in some ways they are the same. But in other ways they are different. Al and Mike are both very strong. Al and Mike both like soccer. But Al plays soccer every day and Mike plays soccer only on weekends. Mike likes watching soccer games on TV but Al only likes to play the game, not to watch it. Al and Mike are both outgoing and funny, but Mike is a little more outgoing than Al. Mike is also a little more serious about school. Al and Mike are very popular at school, and they both have a lot of friends.

根据短文内容判断正误.

    爸爸的微笑消失了，脸色变得严肃起来。他想了一会儿，对儿子和小女儿说：“白杨树从来就这么直。哪儿需要它，它就在哪儿很快地生根发芽，长出粗壮的枝干。不管遇到风沙还是雨雪，不管遇到干旱还是洪水，它总是那么直，那么坚强，不软弱，也不动摇。”

    爸爸只是向孩子们介绍白杨树吗？不是的，他也在表白着自己的心。而这，孩子们现在还不能理解。

烛焰通过凸透镜在另一侧的光屏上成一个倒立放大的像，如果保持凸透镜的位置不变，只将蜡烛和光屏的位置相互交换，那么（   ）