Question

【题目】It may be necessary to stop ______in the learning process and go back to the difficult points in the lessons.
A.at intervals
B.at random
C.at ease
D.at length

Answer 1

【答案】A
【解析】A．at intervals不时；B．at random随意；C．at ease自由自在；D．at length终于。句意：也许在课堂上有必要在学习过程中时不时地停一下回顾难点，故选A。