物质从液态变成气态的过程叫汽化，汽化发生在液体表面的现象叫沸腾（）
参考答案：错
—________did your uncle leave his hometown?
—He ________ for nearly twenty years.
A．When; has left
B．When; has been away
C．How long; has left
D．How long; has been away
若要“向文本文件尾增加数据”，在fopen函数中应使用的文件方式是 ( )
A．"ab+"
B．"a"
C．"ab"
D．"a+"
