[讨论]GWD 8-30，没人问过，是我钻牛角尖了吗？

是不是我没有找到之前的讨论呢？请指教。谢谢！！！

GWD8-30

While Studying the
genetic makeup of corn, a new class of mutant genes was discovered by Barbara
McClintock, a discovery which led to great understanding of cell
differentiation.

A)  a new class of mutant genes was discovered
by Barbara McClintock, a discovery which led to

B)  a new class of mutant genes in corn were
discovered by Barbara McClintock, leading

C)  Barbara McClintock discovered a new class
of mutant genes, and it led

D)  Barbara McClintock discovered a new class
of mutant genes, a new discovery that led

E)  Barbara McClintock, who discovered a new
class of mutant genes, leading

答案据说是d

                

            但是d的a new discovery that led同位谁呢？ a new class of mutant genes也不是一个discovery啊？难道是一种特殊的用法？

            我先选了d，又改了c。c又错在哪里呢？

楼主想看的例子可参考PREP 98. A decade after initiating the nation's most
comprehensive and aggressive antismoking program, per capita consumption of
cigarettes in California declined from over 125 packs annually per person to
about 60, a drop more than twice as great as in the nation as a whole.
(A) per capita consumption of cigarettes in California
declined from over 125 packs annually per person to about 60, a drop more than
twice as great as
(B) annual per capita consumption of cigarettes in
California declined from over 125 packs to about 60, more than twice as great
as that
(C) California's annual per capita consumption of
cigarettes declined from over 125 packs per person to about 60, more than twice
as great as the drop
(D) California has seen per capita consumption of
cigarettes decline from over 125 packs annually to about 60, a drop more than
twice as great as that（D）
(E)
California has seen annual per capita consumption of cigarettes decline from
over 125 packs per person to about 60, more than twice as great as that