VOA慢速英语:American Documents the Country’s First Exchange Students from China

1. The book says China sent one hundred twenty boys to America to learn about developments that could help modernize their country.

learn about 了解
例句：Childrenseem to learn about computers by osmosis. 
儿童似乎不知不觉地就了解了计算机.  
 
2. And we came across this very arresting photograph of a young Chinese boy dressed in what appeared to be traditional Chinese dress.

come across 碰到
例句：If they come across a foreigner, they will combine. 
如果碰到一个外国人，他们就会联合起来。 

3. Mr. Leibovitz said he was lucky to have so much information from events that took place long ago.

take place 发生
例句：Earthquakes take place far underground. 
地震则发生在地球的极深处。 

4. They no longer spoke Mandarin well enough to answer questions.

no longer 不再
例句：He has that prominence no longer. 
他不再拥有那种卓越的地位。