有关燃烧和灭火的说法正确的是（　　）

在做“探究凸透镜成像实验”时，将焦距为10cm的凸透镜和蜡烛放在光具座上，位置如图所示．则在光屏上（　　）

有理数a，b在数轴上对应点的位置如图所示，下列各式正确的是（　　）

Rainforest also help to ____   the weather. When trees are cut down, it gets hotter. Besides, one quarter of our ____  come from plants. Many of these plants can be found only in rainforests. There is a lot that we have not learnt about rainforests. If we____ them, we will never find out.

In my opinion, our future____ saving the rainforests. We must tell more people how important rainforests are so that they will stop doing harm to them. We must protect the rainforests now. We have to act now to save our only home.

下列实验能达到预期目的的是