I'm going to eat more vegetables to keep f__

问题描述:

I'm going to eat more vegetables to keep f__
I'm going to eat more vegetables to keep fit.
I'm going to eat more vegetables to keep fitter.
第一句好(对)还是第二句,为什么?

I'm going to eat more vegetables to keep fit.
这句正确.
我要多吃蔬菜来保持健康.
keep 表示保持某种状态,keep fit 表示保持健康的状态;没有keep fitter这种表达