短文填词根据短文内容和以下提示：1)首字母提示，2)语境提示，3)汉语提示。在每个空格内填上一个适当的英语单词。所填单词要求意义正确，拼写准确。
       We are students of No. 10 Middle School. Recently we have____ (拜访) a paper factory. The paper factory is ____  to the river which gives us ____ (饮用)water. But we found that the factory was p____  waste water directly into the river. Now the water in it is very dirty. Lots of fish have  ____ . Some farmers say that some of their  ____  (羊) and cows have become____   and some have already died ____  they drank the water from the river. So we are  ____  to you to see if you can do something about this. We think the  ____ (污染) must be stopped right now. Thank you!
Yours sincerely，
Mike and John

如图所示，将绿色植物放在暗处一昼夜后，选取一片叶片用不透明的锡箔纸遮盖一部分，放置在阳光下照射几个小时后，取下叶片，去掉锡箔纸，经脱色、漂洗再用碘液处理，结果发现，遮光部分不变蓝色，曝光部分变蓝色．本实验说明：（　　）

①光合作用需要光         ②光合作用需要二氧化碳

③光合作用需要叶绿体   ④光合作用放出氧气

⑤光合作用制造淀粉      ⑥光合作用需要水分．