We use since to talk about an action from some indicated time in the past, up to the present time. Therefore, the present perfect tense of the verb (e.g. has worked) is required. For refers
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We use had to to express an obligation or necessity that existed in the past. We use should have to talk about things that didn’t happen in the past but that we wish had happened.
We can use both needn’t and don’t need to to give permission to someone not to do something in the immediate future. Needn’t have, however, means that the action is completed, but it was unnecessary
We use can or be able to for saying that somebody or something has the ability to do something. We use may or could to talk about the possibility of something in the present or
We often use the past perfect when two things in a sentence happened in the past, and we need to show which thing in the sentence happened first.
We use the present perfect continuous to talk about an activity that started in the past and is continuing now or has recently finished.
The present perfect is often used to talk about situations that started in the past and are continuing now. We sometimes use the present perfect in a question with how long to ask about how
When talking about a life experience, we can use the present perfect. We don’t say when it happened because we’re more interested in the experience, than the time or date.
We use the present perfect for: life experiences in the past, recent past actions that are important now, past situations that are still happening now, and to talk about recent events in the past.
We use used to + infinitive to talk about an action that happened regularly in the past but doesn’t happen now. Used to is different to the past simple because it emphasises that the action