13. When I was a child, I used to jump rope.
我小的時候常常跳繩。
還能這樣說：
When I was young, I used to skip rope.
When I was in the childhood, I always skipped rope.
應用解析：
jump to it 趕快；
jump the gun 過早地行動；
get the jump of sb. 得到超越某人的優勢；
give sb. a jump 嚇某人一跳；
keep one jump ahead of sb. 保持領先于對手的地位
14. Will you jump rope with me?
你愿意和我一起跳繩嗎？
還能這樣說：
Are you willing to skip rope with me?
Shall we jump rope together?
15. It is very interested to watch them jump rope.
看他們跳繩很有意思。
還能這樣說：
It is full of fun to watch them skip rope.
Watching them skip rope is amusing.
應用解析：
watch one's step 謹慎從事；
watch the clock 工作時看表，心不在焉地工作；
keep a close watch on 密切關注；
on the watch for 警戒，注意