鉴别H2与O2两种气体最简便的方法是[ ]
A.将气体通入澄清石灰水
B.用带火星的木条伸入集气瓶里
C.试验气体的溶解性
D.测定气体的密度
答案:B
. Three-fourths of the buildings ______.
A.was destroyed
B.is destroyed
C.were destroyed
D.has been destroyed
发病的内在根据是()
A.正弱邪强
B.邪不可干
C.邪气较盛
D.邪气未退
E.正气不足