prep 161題,求牛人指點迷津一下,拜託！！

Unlike the other major planets, Pluto has a highly eccentric orbit, which is thus closer to the Sun than Neptune is for 20 years out of every year cycle, even though it is commonly described as the remotest planet in the solar system.

A) Pluto has a highly eccentric orbit, which is thus closer to the Sun than Neptune is

B） Pluto has a highly eccentric orbit and is thus closer to the Sun than Neptune is

我選(A)

但答案是(B),原因說(A)的which 修飾 orbit,邏輯不通

我在A and B徘徊,疑問是:

1. 逗號後面的which不一定是修飾最近之名詞orbit,也可以修飾Pluto不是嗎?

2.我不選(B)因為(B)將原句的修飾句升級成為主句的一部份

3.原句沒有因果關係,但(B)有多加一個and,看似變成好像因為highly eccentric orbit然後 closer to the Sun

請大大指點我的錯誤！！拜託  謝謝

超級感謝！！！