单选题
1.Mr. Hall understands that ______ maths has always been easy for him,it is not easy for the students.
A.unless
B.since
C.although
D.when
正确答案:C
答案解析:该题考查连词在宾语从句中的用法。观察题干Mr. Hall understands是主句,其后有that引导的宾语从句,可将该句简化为:______ maths has always been easy for him,it is not easy for the students.分析简化后的句子可知,maths has always been easy for him与it is not easy for the students之间含有转折关系,其他选项不合题干逻辑。故答案为C。