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When to use must have and must of?
We use have to / must / should + infinitive to talk about obligation, things that are necessary to do, or to give advice about things that are a good idea to do. Must and have to are both used for obligation and are often quite similar. They are both followed by the infinitive. I must go now. / I have to go now.
What is the difference between must be and must have been?
It’s simply related to the tense of the verb. “That must be” is present, and can be used for something that has already happened, or that might happened. “Must have been” is past, and cannot be used for something that might happen.
When should must be used?
Must is used to express obligation, give orders and give advice. It can only be used for present and future reference. When the past is involved, you use have to.
When we can use have to?
Use “have to” in the past, present, and future to express responsibility or necessity. NOTE: “have to” is conjugated as a regular verb and therefore requires an auxiliary verb in the question form or negative. We have to get up early. She had to work hard yesterday.
Where do we use need?
Use “need to” to express that something is important for you to do. This form is often used for something that is important one time, rather than referring to a responsibility or duty. She needs to go to Seattle next week. Do you need to get up early tomorrow?
Can we use must have together?
Must or have to followed by an infinitive are used to express obligation. Hence, it doesn’t make sense to use them together.
Can we say must have?
The modal verb must has two past tense forms: had to and must have. Which form we use depends on whether we want to express obligation or if we want to say how certain we are about the probability of something happening.
How do you write must have?
“Must’ve” is simply a contraction of “must have.” Combining the words like this is fine in less formal writing or speech and makes grammatical sense. “Must of,” on the other hand, is almost always a mistake.