They have been skating ______. [ ]A. for three hours ago B. since three hours ago C. three hours ago

题目简介

They have been skating ______. [ ]A. for three hours ago B. since three hours ago C. three hours ago

题目详情

They have been skating ______.
[     ]
A. for three hours ago
B. since three hours ago
C. three hours ago
D. since three hours
题型:单选题难度:中档来源:同步题

答案

B

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