下面哪种献血者通常被认为危险性最小（）。
A.经常献血的无偿献血者
B.偶尔献血的无偿献血者
C.经常献血职业献血者
D.偶尔献血的职业献血者
参考答案：A
枕部外伤后来院行CT检查时突然呼吸节律不整，继之呼吸停止，双瞳等大（）。
A.小脑幕切迹疝
B.小脑扁桃体疝
C.视神经损伤
D.颅内低压
E.原发性脑干损伤
_______ she was standing and waiting for a bus that she caught sight of the former President Clinton.
A．It was while
B．As soon as
C．While
D．During the time when
