气相色谱定性的主要方法有：标样对照定性、利用相对保留值定性、利用保留指数定性等。( )
参考答案：对
I just don’t understand ____that leads to so many teenagers becoming addicted to playing computer games.
A．why it does
B．what it does
C．what it is
D．why it is
24．After the stong earthquake, the local farmers are greatly_________money to rebuild the damaged buildings.
A．in favor of
B．in honor of
C．in want of
D．in case of
