Faced with a difficult math problem, ________．

A.it was given up

B.it was solved by her teacher

C.the girl asked the teacher for help

D.the teacher helped the girl out

答案及解析： C

解析：

Faced with a difficult math problem是分词做原因状语，其逻辑主语应当是主句的主语the girl．即这个女孩面对一道数学难题。