a mountain chain的用法和样例：
- He was pretending to climb a mountain.
- The next day we came to a mountain village.
- He's a mountain climber. he needs good boots.
- A mountain chain of northern Alaska within the Arctic Circle. The northernmost section of the Rocky Mountains, it rises to about 2,7'3 m (9,0'0 ft) in the eastern part of the range.
- I have a mountain of work to do.