乙炔瓶内的乙炔不能用尽要留（）压力的乙炔。
A、0.1MPa
B、0.1～0.2MPa
C、0.2－0.3MPa
D、0.3－0.4Mpa
参考答案：A
However, in ______ recent years, Niagara Falls have come to be appreciated more for their natural beauty as ______ wonder of nature.
A．不填; a
B．the; the
C．不填; the
D．the; a
氨苯砜治疗血管炎的常用剂量（）
A.每日100～150mg
B.每日25mg
C.每日300mg
D.每日400mg
E.每日500mg
