Group 1

Group 2

Group 3

Group 4

Group 5

Group 6

Group 7

Group 8

Group 9

Group 10

Group 11

Group 12

Group 13

Group 14

Group 15

Group 16

Group 17

Group 18

Group 19

Group 20

Group 21

Group 22

Group 23

Group 24

附录1 单元练习答案与解析

附录2 词汇索引