冠桩直径一般不超过（）
A.根径的1／3
B.根径的1／2
C.根径的2／3
D.根径的3／4
E.根径的3／5
参考答案：A
A抗原主要的亚型是（）。
A.A1和A2
B.A2和A3
C.Am和Ax
D.A2和Ax
E.A3和Ax
Don't shout at him. He is unable to hear you because he is _____.[ ]
A. blind
B. deaf
C. hurt
D. burnt
