our friends expected to assume the burden of their own defense,_theg are competent to do.
问题描述：
our friends expected to assume the burden of their own defense,_theg are competent to do.
which we are certain
that we are certain of
of which we are sure
for which we are sure
for which we are sure
答
这里是把of 提前了~把它理顺就是：which we are sure of.这里be sure of 是固定搭配,意思是："对……表示肯定" ,再有,这个句子是很典型地考察定语从句的用法.首先,横线前面有个逗号,逗号后面不能用that ,所以B排除....