31-35 DCDAA 36-40 ADDAA 41-45 DBCCB 46-50 CDBDC 51-53 CAC 54-56 BAD 57-60 BDAC 61-65 BBDDC 66. four materials 67. Special machines and printing skills. Wood and graphite. Is glue natural or man-made 我们生活在一个人造物品的世界里。 the 72. seventh 73. had 74. about 75. better seconds 77. happily 78. what 79. worked 80. us What fine weather it is! What can we do after school Let’s go to the park. There are many children playing games. We can’t walk on the grass.
