【题目】Since the new speed limits ________, the number of accidents in the area has fallen strikingly.
A．were introduced
B．introduced
C．have been introduced
D．have introduced
在线课程【答案】A
【解析】考查时态和语态。句意：自从新的速度限制被提出，这个区的交通事故数量下降了很多。speed limits与introduce之间为被动关系，而且事情发生在过去，故用过去时态的被动式，故选A。