不能用来鉴别一氧化碳和二氧化碳两种气体的方法是（ ）
A．观察颜色
B．通入紫色石蕊试液
C．通入澄清的石灰水中
D．点燃
答案：A
-They say Philip's brother is a billionaire.
-________? He wouldn't accept any help from his brother, even if it were offered. [ ]
A. What if
B. What for
C. So what
D. Forget it
法律行为一定是有效行为。( )
