问题
选择题
At a construction site in our city the workers have uncovered an ancient wall that_______ to keep the enemy out of the city, but it requires further evidence.
A．might have functioned
B．would have functioned
C．must have functioned
D．should have functioned
答案
A
考查虚拟语气。might have done 意为“过去可能是做什么的”，是对过去肯定的猜测。句意为：在市里的一处工地上，工人们挖出了一道以前可能是用来御敌的城墙，但这还有待进一步验证。根据句意选A。