题目

_____twice a year, whether it is a car or a bus or a truck, is the rule that every driver must obey in this city. A．Being examined                       B．Examined C．Examining                          D．Having been examined 答案：A杏的果实中可食用的部分是由杏花中的哪个部分发育来的A. 子房 B. 胚珠 C. 珠被 D. 子房壁