We slept on the hard ground, ate canned beans from cold metal plates and spent our days in the difficult search for gold.

VOA: special.2009.07.04

Why has it been so hard and why does it continue to be difficult to identify these pluripotent cells within tissues?

为什么会那么难呢,为什么在组织中识别多能干细胞,始终困难重重呢

耶鲁公开课 - 生物医学工程探索课程节选

This proves to be really difficult in the real world because in the real world it's hard to pull apart genes and environments So, you and me will have different personalities ? Why?

这在现实中是很难区分的,因为现实中很难,把基因和环境分开来讲,你和我有不同的性格,为什么？

耶鲁公开课 - 心理学导论课程节选

But the work is hard. And getting all the oil from the seeds can be difficult.

VOA: special.2009.09.29