Ⅴ.选择填空：从A、B、C中，选出一个最佳答案完成句子。
17. Nowadays people care more about the safety of . Everyone wants to eat healthily.
A. foods B. clothes C. houses
18. Emma, can you introduce _______ to Alice? I want to make friends with her.
A. him B. her C. me
19. -- Nothing in the world is ________ if you put your heart into it.
-- I agree. You’ll succeed if you work hard.
A. important B. impossible C. necessary
