Unit 1 Period 2 Grammar课件 牛津版必修2
Unit 1 Period 2 Grammar课件 牛津版必修2第3页

The present perfect tense

The present perfect tense is normally used for an action which lasts throughout an incomplete period, and in this case, we often use such time expressions as for, since, all day/night/week, all the time, always, lately, never and recently.