b.不定式:to+动词原形 3.动名词做主语 Getting enough vitamins is essential to life. 解析:这句话简化之后就变为A is essential to life. 注意一下:A is essential to B的意思是:A对于B 来说很必不可少。 A所代表的这个Getting enough vitamins中通过它出现的位置是...