问题

Some of the students are not sure ___ spelling the word, while others are not sure ___ the use of some grammatical rules
A:of… about
B:about…to
C:of…to
D:for…of
B:about…to
C:of…to
D:for…of
正确答案是:
同类题型
Had I known about this computer program, a huge amount of time and energy ________. [ ]
.— _____does she exercise— Once a week.
The company a rise in salary for ages but nothing has happened yet. [ ]
His son is very naughty and has formed some bad habits.I think he should .
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