1．By ________(不屈不挠)，the disabled boy learned how to swim.
2．We need to establish the legal ________(结构)for the protection of the environment.
3．The children ________(涂黑) their faces with charcoal and began to play games.
4．Water the plants r________，and never let the soil dry out.
5．He tried to g______ anything that might help him.
