21
[答案]:A
[解析]:参见教材P282
22
[答案]:B
[解析]:参见教材P275
23
[答案]:A
[解析]:参见教材P275
24
[答案]:D
[解析]:参见教材P276
25
[答案]:C
[解析]:参见教材P277
26
[答案]:B
[解析]:参见教材P278
27
[答案]:C
[解析]:参见教材P280
28
[答案]:D
[解析]:参见教材P281
29
[答案]:B
[解析]:参见教材P281
30
[答案]:A
[解析]:参见教材P281
31
[答案]:C
[解析]:参见教材P282
32
[答案]:B
[解析]:参见教材P272
33
[答案]:B
[解析]:参见教材P275
34
[答案]:A
[解析]:参见教材P281
35
[答案]:C
[解析]:参见教材P283
36
[答案]:A
[解析]:参见教材P272
37
[答案]:B
[解析]:参见教材P272
38
[答案]:C
[解析]:参见教材P273
39
[答案]:B
[解析]:参见教材P279
40
[答案]:D
[解析]:参见教材P279