请教一道语法题

com198

The astronomical units is the average distance of the Earth from the Sun___is the standard of distance in the Solar system.

(A)and

(B) also

(c)in addtion

(d)because

答案是A,为什么B不对?

com198

可是空格后面没有主语阿

com198

4楼的MM和我一样起这么早啊!

还有一题:

Art Deed, a style of design popular in the 1920's and 1930's, was used primarily in furniture, jewel, textiles, and interior decoration.

不太理解design在这里做名词用,popular是adj,是不是应该改成popular design合理一点?

com198

TOEFL中的定语从句省略是不是很多？