下图中反映的历史事件直接造成了农村社会生产力的极大破坏的是 [ ]
A.1952年土地改革
B.1954年农民入社
C.人民公社化运动
D.家庭联产承包
答案:C
Excuse me, Marcia, a reporter from Vanity Fair ________ all day. Could you speak to her now?
A.phones
B.has phoned
C.has been phoning
D.phoned
试说明引发剂浓度从哪些方面对聚合度产生影响?