The post-World War II baby （）resulted in a 43 percent increase in the number of teenagers in the 1960s and 1970s.

These continual （）in temperature make it impossible to ...

单项选择题These continual （）in temperature make it impossible to decide what to wear.

In mountainous regions, much of the snow that falls is ...

单项选择题In mountainous regions, much of the snow that falls is （）into ice.

The boxer （）and almost fell when his opponent hit him.A...

单项选择题The boxer （）and almost fell when his opponent hit him.