Many say they are now out of work, and they worry for how long.

VOA: standard.2010.06.01

As time increases, the angle increases and we can ask, "How long does it take for the particle to come back to the starting point?"

这个角度随着时间在增加,我们会问,"质点需要多长时间,才能转到起点"

耶鲁公开课 - 基础物理课程节选

" And-- "How long are you going to stay happy for?"

你们的快乐会持续多久“

哈佛公开课 - 幸福课课程节选

"I was one of these teenagers, and so I know how difficult it can be to break this habit when it's been with you for a long time,".

VOA: standard.2009.06.22

" And-- "How long are you going to be devastated for?"

那你们会痛苦多久“

哈佛公开课 - 幸福课课程节选

That's how long it took for an international team of scientists to excavate and analyze the fossilized skeleton of a 4.4 million year old human ancestor, Ardipithecus ramidus, which was discovered in Ethiopia.

VOA: standard.2009.12.24