单词拼写：根据下列各句句意和空白之后的汉语提示词，写出对应单词的正确形式，每空只写一词。

1. She was brought into hospital for _________ (观察).

2. I always __________ (后悔) that I never trained.

3. __________ (不幸), he lost two of his family in the earthquake.

4. Because of the bad weather, many _________ (航班) have been called off.

5. When the earthquake broke out, we can find everything in the house _________ (摆动) without stop.

若地球上无大气层，下列现象不再存在的是[ ]

A、蓝蓝的天空白云飘

B、月有阴晴圆缺

C、烈日炎炎似火烧

D、繁星纷呈