Tom didn't go to school this morning because he overslept.
A. at once
B. on time
C. by accident
D. at present
网友回答
A. at once
(答案→)B. on time
C. by accident
D. at present
解析:考查词语辨析。at once “立刻;马上”;on time“按时”;by accident“偶然”;at present“目前;现在”。句意为“汤姆今天早晨没有按时上学,因为他睡过了头”故选B.