Question

【题目】The teacher spent a long time _____ the problem to the boys after class. (解释)

Answer 1

【答案】explaining

【解析】

句意：下课后，老师花费了很长时间向孩子们解释了这道难题。
解释：explain。spend...(in) doing sth. 花费……做某事。此处动名词作宾语，介词in可省略。故答案为explaining。