that is引导定语从句什么情况下省略？

zdytiffany

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 by 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 by the 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
E.which occurred not just because of more expensive drugs but because doctors have also written

答案是B

但是之前有的题目解释说that is很罗嗦，要去掉… 这会又保留了，困惑。虽然其它选项很容易排除。

yorku

that is、who is+n/ved/ving/adj等将that is、who is省略属于concision的范围，只有将其他的grammar问题一一排除后，若只剩下二选一时，才会采用concision优选更加简练的易懂的选项，所以罗不罗嗦，都不可以是直接排除选项的依据，要先考虑meaning+grammar

yorku

再说这道题。。。。很明显a phenomenon的同位语结构优选啊。。。。。。

zdytiffany

嗯… 有道理。谢谢大牛