许国璋主编英语第1册 1979年重印本 练习答案PDF电子书下载

Lesson Thirteen 1

Lesson Fourteen 4

Lesson Fifteen 7

Lesson Sixteen 10

Lesson Seventeen 14

Lesson Eighteen 16

Lesson Nineteen 20

Lesson Twenty 23

Lesson Twenty-One 27

Lesson Twenty-Two 31

Lesson Twenty-Three 35

Lesson Twenty-Four 40