能区分氧气和氮气的化学方法是 [ ]
A．气味不同
B．是否能使带火星的木条复燃
C．密度不同
D．是否能使澄清石灰水变浑浊
答案：B
—Charlie has been nowhere for three days. What has happened to him?
—Didn’t you know he had gone to Hong Kong?
A．in sight
B．in place
C．in face
D．in use
休止时间
