关于that做主语的问题 谢各位！

393075583

旧prep sc90

90.(29431-!-item-!-188;#058&003914)

Archaeologists in Egypt

have excavated a 5,000-year-old wooden hull that is the earliest surviving example of a "built" boat--in other words, a boat constructed out of planks fitted together--and that thus represents a major advance, in terms of boat-building technology, over the dugout logs and reed vessels of more ancient vintage.

(A) together--and that thus represents

(B) together--and this has represented

(C) together, and it represents

(D) together that was representing

(E) together to represent

A选项是答案，可是and that thus represents..... 这里that不是做主语了吗？
什么情况下that可以做主语，什么时候不可以呢？

花子落落

和前一个that并列，共同修饰hull

393075583

和前一个that并列，共同修饰hull

-- by 会员 花子落落 (2010/8/18 23:02:32)

thank you~
我后来也发现 这题我问得有点白痴了