在make sure(弄清楚)以及make certain(弄清楚)后接that从句时，从句谓语通常用一般现在时表示将来意义（而不直接使用一般将来时）。如：Make sure you come back soon. 你要保证快点回来。Make sure you sign and date it at the bottom. 一定要在底下签名和写上日期。Make certain that you do not spill your coffee. 注意不要洒泼了咖啡。Make certain that you lock the door if you go out. 你出门时要记住把门锁好。