Lesson 1 1
Lesson 2 2
Lesson 3 4
Lesson 4 6
Lesson 5 8
Lesson 6 10
Lesson 7 12
Lesson 8 15
Lesson 9 18
Lesson 10 22
Lesson 11 25
Lesson 12 28
Lesson 13 31
Lesson 14 35
Lesson 15 38
Lesson 16 42
Lesson 17 47
Lesson 18 53
Lesson 19 57
Lesson 20 61
参考答案 65