问题
选择题
.Mr. Black has been teaching English in a middle school _____ he came to China.
A．for ever
B．ever since
C．ever before
D．long before
答案
答案：B
题目分析：考查固定词组：A. for ever曾经，B. ever since自从，C. ever before以前，D. long before很久以前，句意：自从布莱克先生到中国来一直在中学教英语。和ever since+从句，连用的主语是现在完成时，选B。