So-called green taxes, which exact a price for the use of polluting or nonrenewable fuels, are having a positive effect on the environment and natural resource base of countries as varied as China, the Netherlands, and Hungrary.
a. as varied as
b. as varied as are
c. as varied as those of
d. that are as varied as
e. that are as varied as are
答案a
疑问是前面明明说的是the environment and natural resource base of countries,为什么不是C中的those of 呢?