It's important _______us to learn a second language_______our mother tongue.

问题描述:

It's important _______us to learn a second language_______our mother tongue.
A.for,besides B.for,except C.to,except D.to,besides

B
it is +形容词+for/of sb to do sth
for,固定句型
except出了.之外(不包括)
besides(包括的意思)