OG13 SC 86题，分析不出主句的主谓宾结构，求助！！！
86.
In 2000, a mere two dozen products accounted for half the increase in spending on prescription drugs, a phenomenon that is explained not just because of more expensive drugs but bv the fact that doctors are writing many more prescriptions for higher-cost drugs.
(A) a phenomenon that is explained not just because of more expensive drugs but by the fact that doctors are writing
(B) a phenomenon that is explained not just by the fact that drugs are becoming more expensive but also bythe fact that doctors are writing
(C) a phenomenon occurring not just because of drugs that are becoming more expensive but because of doctors having also written
(D) which occurred not just because drugs are becoming more expensive but doctors are also writing
答案是B，没有疑问，坛子里有几个帖子都是讨论这题的。
请各位NN分析一下题干中的句子主干结构，主谓宾分别是什么。
a phenomenon that，that引导的应该是同位语从句吧，这样的话a phenomenon开头的是主句？还是逗号前的句子是主句？
当逗号前的句子是主句的时候，a phenomenon又是什么成分？
多谢！ |
