[問題]真題一道

[bmwbenzfan]

Question

Roman building was made possible by the discovery of cement which would harden underwater, making it far superior to the lime mortar that had been previously in use.

(A) cement which would harden underwater, making it far superior to the lime mortar
(B) the hardening of cement underwater, far superior to the lime mortar
(C) the way in which cement would harden underwater, making it far superior to the lime mortar
(D) cement which, hardening underwater, made it far superior to that of the lime mortar
(E) the hardening of cement underwater, made it far superior to that of the lime mortar

正確答案是(A)

這題考硬梆梆比較。我一開始看不懂句意，以為" it" 代替的是Roman building。 我的問題就是，為什麼"it" 不是代 主詞Roman building?
我是剛起步的新手，常聽人家說代名詞優先代原體主詞，但我不知道原體主詞是什麼? 哪位高手願意分享，願聞其詳。