再问prep178 看了解释也没有懂

178.
                More than 300 rivers drain into Siberia's Lake Baikal, which holds 20 percent of the world's fresh water, more than all the North American Great Lakes combined.

(A)More than 300 rivers drain into Siberia's Lake Baikal, which holds 20 percent of the world's fresh water, more than all the North American Great Lakes combined.

B. With 20 percent of the world's fresh water, that is more than all the North American Great Lakes combined, Siberia's Lake Baikal has more than 300 rivers that drain into it.

C. Siberia's Lake Baikal, with more than 300 rivers draining into it, it holds more of the world's fresh water than all that of the North American Great Lakes combined, 20 percent.

D. While more than 300 rivers drain into it, Siberia's Lake Baikal holds 20 percent of the world's fresh water, which is more than all the North American Great Lakes combined.

E. More than all the North American Great Lakes combined, Siberia's Lake Baikal, with more than 300 rivers draining into it, holds 20 percent of the world's fresh water.

我不明白为什么A正确，这句话里边，主句就没有动词啊，完全不明白再说什么，请哪位高人指点一下！

窃以为:

这句是挺抽象的,不过动词还是很清楚呀 drain吧

我的愚见：

A：300条河流入SLB，which用来修饰SLB，说明SLB占有世界上20％的淡水，比北美其他所有湖合在一起都要多

B：句子结构混乱

C：句子结构混乱

D：使用了while，显然改变了原句的语气

E：more than放在句首，和SLB搭配，逻辑意思不通。