麻醉性镇痛药引起呼吸抑制时的最佳拮抗剂是（）
A.吗啡
B.烯丙吗啡
C.纳洛酮
D.哌替啶
E.可待因
参考答案：C
为什么封塔时间不能太长？
Annie Jump Cannon, ________ discovered so many stars that she was called "the census taker of the sky".
A．a leading astronomer,
B．who, as a leading astronomer,
C．was a leading astronomer,
D．a leading astronomer who
