有谚语云:“白露早,寒露迟,秋分种麦正当时。”说明了24节气对农业生产的指导意义。你知道人们测定出一年24个节气是在何时吗?[ ]
A.夏朝
B.商朝
C.战国
D.西周
答案:C
下列材料属于复合材料的是( )
A.聚乙烯
B.机动车轮胎
C.不锈钢
D.青花瓷
There is a police car in front of our neighbor's house. What do you suppose ______?[ ]
A. did happen
B. has happened
C. is happen
D. has been happened