Unit 1 1
Unit 2 12
Unit 3 24
Unit 4 36
Unit 5 48
Unit 6 61
Unit 7 73
Unit 8 86
Unit 9 100
Unit 10 114
附：参考答案 127
Key to Unit 1 127
Key to Unit 2 129
Key to Unit 3 132
Key to Unit 4 135
Key to Unit 5 138
Key to Unit 6 140
Key to Unit 7 142
Key to Unit 8 144
Key to Unit 9 146
Key to Unit 10 148
References 150