题目

Imagine that you are running in a park on a very hot day. Will you feel tired? The answer is yes. But besides【1】 feeling of being tired, I believe most people will feel thirsty soon. You will feel much【2】（good）right away after you drink some water. Your body needs water, so it tells you to drink. It's simple, right?Actually, it's not【3】（real）simple. There is a special part in our brains. When our blood is too salty, it says, Drink! 【4】 we drink, it is quiet. Water does not go into our blood right away. However, our brains still know that we【5】（drink）before. How?一列火车自2013年全国铁路第10次大提速后，速度提高了26千米/小时，现在该列火车从甲站到乙站所用的时间比原来减少了1个小时。已知甲、乙两个车站的路程是312千米，设火车提速前的速度为x千米/小时，根据题意所列方程正确的是(     )A．- =" 1"B．- = 1C．- = 1D．- = 1