1.a beam of (light) 一束（光）

例句:Reflection of a beam of light on the diaphragm falls on a phototransistor.
经膜片反射的光束照射到光敏管上。

2.a big shot 大人物

例句:He acts like a big shot, but he is just a small potato.
他行事象个大人物,但实际上他却微不足道。

3.a big sale 大减价

例句:Lose no time in buying a real bargain at the big clearance sale.
趁清货大减价，快买便宜货。

4.a bunch of 一束，一串，一群

例句:He produced from his pocket a bunch of keys.
他从口袋里掏出一串钥匙。

5.a cloud of 一大群；一大片

例句:A cloud of suspicion still hung over the White House.
白宫上空仍笼罩着一团疑云。

6.a couple of 一对，一双；几个

例句:Selection is a pretty simple concept, but there are a couple of basic variants worth discussing.
选择是相当简单的一个概念，但有一些变体值得我们来讨论。