生态学的发展概括起来，分为 ( )
A．三个时期B．四个时期C．五个时期D．六个时期
参考答案：B
燃放鞭炮给人身和环境带来危害，北京市发生禁放令，禁止燃放的标志是（ ）
A．
B．
C．
D．
—I hear Tom ______ playing games recently.
—______ no wonder he is easy to feel sleepy in class.
A．is addicted to；There is
B．addicts；There is
C．addicts；It is
D．is addicted to；It is
