求高手指导几道英语选择题...关于名词部分的

We should look up to him as a shinning example of ____ to duty.
A devotion B privilege C responsibility D burden
只是普通的负责,就不是shining example了,每个人都应该负自己的责任,devoation to duty 是为自己的职责而献身...这就不一般了..
AIDS control and prevention is a ____ to China as well as the whole world.
A surprise B challenge C reaction D threat
答案是B,可是我觉得D更好吖...想不通吖...
控制和防御艾滋病是一个很大的挑战.
怎么会是威胁呢?
This is an old photo of my mother when she had ___ ,and now she has ____.
A short hair:grey hairs
B short hairs :grey hair
C short hair:grey hair
D short hairs:grey hairs
答案是A,可是我选的是B,根本就是反的,到底hair 的用法是什么样的啊...犯迷糊了...
发型用hair.hairs 是说她现在头发斑白了...（有灰白的头发了）
如果你说..my hair is grey.是说我头发颜色是灰的（很可能是染的）
Would y0u be so kind as to give me a ___?I'm too tired to walk any further.
I'm sorry,but the car is too crowded.
A place B drive Cseat D lift
答案是B啦,可是我记得D似乎也有搭便车的用法吖...哪位大侠可以指导一下咯...
give a lift 是有顺便帮忙的意思,但不一定是搭车,要看上下文,这里如果没有drive,可以选这个...不过这里最佳答案是B.....