.We cannot figure out ____quite a number of insects, birds, and animals are dying out.
25. The train leaves at 6:00 p.m., so I have to be at the station ____ 5:40 p.m. at the least.
24. --- How did you go to work yesterday? --- I went to work _____ my friend’s private car.
23. It is said that a bridge is being built _____ the river.
22. We will never forget this historical lesson written _____ blood.
21. He is very strict with others, but he is always blind _____ his own shortcomings.