a. He must be very old. Look，he has grey ________.

b. He found some ________ in his soup.

 A. hair，hair                 B. hairs，hairs                C. hair，hairs                 D. hairs，hair

此题应选 C，容易误选 A，误认为hair永远不可数。其实hair这个词既可以是可数名词，也可以是不可数名词，只是含义稍有变化：

1. 作为可数名词，是指一根一根的“头发”或“毛发”：

Look at this, a hair in my soup. 你瞧，我的汤里有根头发。

The cat has left her loose hairs all over my clothes. 猫掉的毛弄得我衣服上到处都是。

My father has quite a few gray hairs. 我父亲已有不少白发。

There is not a gray hair on his head. 他头上没有一根白头发。

2. 作为不可数名词“头发”的总称，是集合名词：

I’ll have my hair cut. 我要去理发。

He has blond hair. 他有一头金发。

She has a beautiful head of hair. 她有一头漂亮的头发。

The woman likes to do her hair in foreign style. 这个女人喜欢把头发梳成外国式。

试比较以下句子：

He has grey hair. 他满头白发。

He has grey hairs. 他有些白发了。