无菌溶液打开未用完，消毒瓶口、瓶塞后盖好，其有效保存期是（）。
A.4小时
B.24小时
C.3天
D.7天
E.20天
参考答案：B
World War Ⅱ is commonly acknowledged ______ some of the 20th century's most notable poetry.
A．and produced
B．to produce
C．to have produced
D．had produced
土地使用权的出让
