再生障碍性贫血引起的鼻出血（）
A.血小板异常
B.血小管损伤
C.破坏造血系统
D.内源性凝血酶原减少
E.外源性凝血酶原减少
参考答案：A
—They are quiet, aren’t they?
—Yes. They are accustomed ________ at meals.
A．to talk
B．to not talk
C．to talking
D．to not talking
下列属于HLA复合体的非经典Ⅱ类基因的是（）
A.HLA-DM
B.HLA-DN
C.HLA-DO
D.HLA-DR
E.HLA-DP
