求助：关于因果关系并列句和伴随状态

95.  (29661-!-item-!-188;#058&003962)

Unlike frogs that metamorphose from tadpoles into adults within a one-year period, it takes three to four years for the mountain yellow-legged frog of the Sierra Nevada to reach adulthood, and so they are restricted to deeper bodies of water that do not dry up in summer or freeze solid in winter.

(A) it takes three to four years for the mountain yellow-legged frog of the Sierra Nevada to reach adulthood, and so they are

(B) it takes the mountain yellow-legged frog of the Sierra Nevada three to four years until it reaches adulthood, and therefore it is

(C) in the Sierra Nevada, mountain yellow-legged tree frogs take three to four years to reach adulthood, thus being

(D) mountain yellow-legged frogs of the Sierra Nevada take three to four years until they reach adulthood, thus

(E) mountain yellow-legged frogs of the Sierra Nevada take three to four years to reach adulthood, and so they are

PREP语法说：

（C）错。

1）应该将比较物mountain yellow-legged tree frogs 放在句首（这点我理解）

2）being 多余，可以直接用过去分词做伴随状态（这点也理解）；但是，即使正确使用伴随状态，也是错的。

因为这两个动作并不是同时发生的，是有因果关系的，前一个动作导致了后一个动作，所以要使用因果关系并列句来表示。即E，....and......

这想问的是：1）并列句中前后两个不是同时发生的吗，还可以表示因果关系吗

                        2）伴随状态不能表示前后有因果关系吗

请指教！谢谢啦

1.这里用了and so连接 关键在so

2.伴随是指从句的伴随 可以表示前面一句的结果 主语要一致 都是同一个东东或人发出的