Unit one 1
Unit Two 2
Unit Three 4
Unit Four 6
Unit Five 8
Unit Six 10
Unit Seven 12
Unit Eight 14
Unit Nine 16
Unit Ten 18
Unit Eleven 20
Unit Twelve 22
Unit Thirteen 24
Unit Fourteen 26
Unit Fifteen 28
Unit Sixteen 30
Unit Seventeen 32
Unit Eighteen 34
Unit Nineteen 36
Unit Twenty 38
Unit Twenty-one 40
Unit Twenty-two 42
Unit Twenty-three 44
Unit Twenty-four 46
Unit Twenty-five 48
Unit Twenty-six 50
Mid-term Test 52
Final Test 54
音带文字 56
参考答案 90