请教几道语法题

gongbo84321UID: 197894

1. The most important chemical catalyst on this planet is chlorophyll, -------carbon dioxide and water react to form carbohydrates.
(A) whose presence
(B) which is present
(C) presenting
(D) in the presence of which   
A:D     怎么做出来的呀?
2.__ over 100 years since the invention of the square-bottomed paper bag.
(A) Now is
(B) Now it has
(C) There is now
(D) It is now
A:D 但是c为什么不对?
3. The distinguishing feature of a fluid, in contrast to a solid, is the ease _____ .
(A) that a deformed fluid
(B) to deform a fluid
(C) when a fluid that is deformed
(D) with which a fluid may be deformed
A:D  和第一题一样,不知怎么做.
4. The( poor) condition of( prisoners are )what (concerned) Dorothea Dix, an American social worker and( director of) a school in Boston.
A:D 知道选b,但  c为什么不对?
5.Under (the certain) conditions, a rainbow appears at the end (of) a (rain shower) (in the quarter) of the sky opposite the Sun.
答案有两种
谢谢,需要详细解答.

reliveUID: 2160214

DDDBA
对吗 ？

gongbo84321UID: 197894

D 都成了:D     :)    :)   :)

gongbo84321UID: 197894

2楼   对,但我要解释.答案我已经知道了谢谢.