求助几道语法题目！

Huhoo

1。（98年1月份）
(In) the 19th century, North American locomotives (ran )on hardwood (fuel), which was (inexpensive) and plentiful in the time.
答案是D，为什么那？

2。（9910）
Collagen, a (strong) rubbery protein, (supports the) ear flaps and the tip (of nose) in (humans.)
答案是D，为什么不是c那？nose是可数名词呀，而且human也是可数名词。

braveMBA

1. 好象划线应该在in the time--- at the time(在那时候)

2. 因为tip用了单数，没有划线，就确认了单数的形式，所以humans --- a human

Huhoo

thanks a lot! I got it!