覆盖义齿的组成不包括（）。
A.人工牙
B.基托
C.卡环
D.固位体
E.连接体
参考答案：C
驾驶机动车在这种山区弯道怎样转弯最安全？
A、靠弯道外侧行驶B、减速、鸣喇叭、靠右行C、借用对向车道行驶D、靠道路中心行驶
— Did you know any Chinese before you arrived in Beijing?
— Never ________ it, actually.
A．had I learned
B．have I learned
C．I have learned
D．I had learned
