Question

【题目】— Did Cathy have problems ________ out the problems?
—Yes. I found her _________ on it for nearly half an hour.
A.work; to work
B.to work; working
C.working; working

Answer 1

【答案】C
【解析】句意：—凯西解决这些问题有困难吗？--—是的。我发现她做了将近半个小时。have problems(in) doing sth. 做某事有困难， find sb. doing sth.发现某人正在做或持续做某事，结合句意，答案为C。