I didn't understand until he（ ）on the question.

I didn't understand until he（ ）on the question.
A、showed
B、elaborated
C、devised
D、simplified
【正确答案】：B
【题目解析】：本题考查动词辨析。show“展示”， elaborate“详细描述”， devise“设计”， simplify“简单化”。句意：直到他详细解释了这个问题，我才明白。故选B。