问题
选择题
The doctor must be _______ 24 hours a day, 7 days a week in the boarding school.
A．on call
B．by hand
C．in sight
D．on spot
答案
答案：A
题目分析：考查介词短语：A. on call随叫随到，待命，B. by hand在手边，C. in sight在视野以内，D. on spot在出事地点，句意：在寄宿学校，这个医生必须一星期7天一天24小时待命。选A。