Smoking causes some health problems ---in fact far more serious___than mobile phones do.

问题描述:

Smoking causes some health problems ---in fact far more serious___than mobile phones do.
A.one B.it C.ones D.those
望给个详解

C
代的是health problems 复数,排除 A,B
those 不能有前置定语,只可有后置定语,所以这里不能用