【单选题】C In most situations, light helps us see. But nowadays humans are using too much of it so that it is in fact a kind of pollution. When it comes to looking at the night sky, too much light makes it dif...
【简答题】A.Planktons are too small to be seen. B.Most planktons have transparent tissues. C.Most planktons are practically invisible to predators. D.Planktons are fascinating organisms.