18. E: line 4-7, you can grasp it by adding "being" before the sentence. 19. E: line 23-25, "safety valve" 20. line 30 "social structure". I do not know why the correct answer is B 罗马题is my headache. 21. B: line 11 "a person", 对although取反。(ets总是标新立异的嘛) 22. A: line 45-49.干扰项E 23. D: line 44 "sectional conflicts"