The car must have been doing at least 100 miles an hour.
这车速肯定每小时至少100英里。
Biological systems have been doing this for billions of years
生物系统亿万年来一直都是这样。
Some scientists have been doing research on artificial internal organs.
一些科学家一直在研究人造内脏。
So, what have you been doing today?
那你今天都干什么了？
What have you been doing this week?
你这个星期都在做些什么？
