21
[答案]:B
[解析]:参见教材P236
22
[答案]:C
[解析]:参见教材P235
23
[答案]:C
[解析]:参见教材P238
24
[答案]:D
[解析]:参见教材P238
25
[答案]:C
[解析]:参见教材P238
26
[答案]:B
[解析]:参见教材P239
27
[答案]:B
[解析]:参见教材P209
28
[答案]:D
[解析]:参见教材P211
29
[答案]:B
[解析]:参见教材P213
30
[答案]:B
[解析]:参见教材P215
31
[答案]:A
[解析]:参见教材P231
32
[答案]:C
[解析]:参见教材P205
33
[答案]:B
[解析]:参见教材P209
34
[答案]:B
[解析]:参见教材P209
35
[答案]:C
[解析]:参见教材P210
36
[答案]:A
[解析]:参见教材P212
37
[答案]:C
[解析]:参见教材P217
38
[答案]:B
[解析]:参见教材P219
39
[答案]:A
[解析]:参见教材P225
40
[答案]:B
[解析]:参见教材P226