ABO血型系统中的A型血是指()
A.红细胞表面有A抗原
B.白细胞表面有A抗原
C.血小板表面有A抗原
D.血清中有A抗原
E.血清中有抗A抗体
参考答案:A
期权交易的卖方负有必须履约的义务。()
— Hi, David, I heard you had an accident this morning.
— Yes. Luckily, I hit the brakes in time ______ I would have been injured badly. [ ]
A. and
B. but
C. or
D. so