(1)可表示客观真理、科学事实。
The sun rises in the east and sets in the west.
太阳从东方升起，从西方落下。
(2)可用在由if，unless引导的条件状语从句，由even/if/though引导的让步状语从句，由when，before，until/till，as soon as，the moment引导的时间状语从句，由no matter what/who/when/where/how或whatever，whoever等引导的让步状语从句中，这时主句往往表将来或主句是祈使句。
I’ll go with you as soon as I finish it.
