在正常情况下，爆炸性混合气体连续地、短时间地频繁出现或长时间存在的场所为（）区。
A、1
B、2
C、3
D、0
参考答案：D
用所给单词的适当形式完成句子。
1. Is it right _______ (experiment) on animals?
2. What's the ________ (mean) of this? Why have you left your clothes untidily on the floor?.
3. We hired two rooms with _______ (connect) doors.
4. We are collecting _______ (donate) for the homeless children.
5. Our teacher __________ (communicate) his ideas very clearly.
一主子午线聚焦在视网膜上，另一主子午线聚焦在视网膜之前成为()
A．单纯近视散光
B．单纯远视散光
C．复合近视散光
D．复合远视散光
E．混合散光
