B.How many times
Only once只一次.
自然是问:去过多少次?
A.How often 是问频度的,多久去一次._____you be able to work out this Maths problem by yourself? A.Will B.Are C.Can D.Could选什么A你能独立做出...吗? be able to用了原形,已经有BE了.所以B不对.can =be able toC和D不对.