“I know she was in because I heard her radio, but she didn’t open the door.” “She___the bell.”

A．may not be hearing

B．may not have heard

C．must not have heard

D．must not be hearing

用化学用语填空：

（1）金刚石______．（2）碳酸氢铵______．

（3）氢氧根离子______．（4）氧化铝中铝元素的化合价______．

（5）天然气（沼气）的燃烧反应______．