250-27

27.In 1929 relatively small declines in the market ruined many speculators having bought on margin; they had to sell, and their selling pushed other investors to the brink.
(A) speculators having bought on margin; they had to sell, and
(B) speculators who had bought on margin; having had to sell,
(C) speculators who had bought on margin; they had to sell, and
(D) speculators, those who had bought on margin; these speculators had to sell, and
(E) speculators, who, having bought on margin and having to sell.

答案是C  我想請問一下  C裡面的THEY 為什麼  沒有優先指代的問題

因為如果有優先指代  they應該是指declines 不是嗎???

對於指代的用法  非常疑惑  ????