在我国封建社会，文字狱规模最大、次数最多的是[ ]
A．秦朝
B．汉朝
C．元朝
D．清朝
答案：D
He ________ more than 5,000 English words when he entered the university at the age of 15.
A．has learned
B．would have learned
C．learned
D．had learned
小机油系统启动前为什么应先开启直流油泵？
