Of the twin supernovas, the most recently discovered is the largest, but it is the small one that has irrevocably altered astronomists’ ideas about the origins of the universe.

(A) the most recently discovered is the largest, but it is the small one

(B) the one most recently discovered is the largest, but it is the small one

(C) the most recently discovered is larger, but it is the smaller

(D) the more recently discovered one is the large one but the small one（E）

(E) the more recently discovered is the larger, but it is the smaller one

居首的Of在这里是什么意思，什么用法啊，我查longman内容太多了，搜不出来

谢谢