What is the difference between "must" and "have to"?

[Solovey]

Test No. incompl/elem-7 "Modals", question 5

Do you ......... clean the house every day or every week?

(a) must
(b) have
(c) have to

Test No. incompl/elem-7 "Modals", answer 5

Do you have to clean the house every day or every week?

Correct answer: (c) have to

Your answer was: incorrect
Do you must clean the house every day or every week?
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Why it is so?

Solovey

[Torsten]

When we use the modal verb must in a question we don't need the auxiliary verb (help verb) do/does.

For example:
Must you speak so loudly? Can't you see I'm working?
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary

[Lisa_Mard]

"must" can not use "do"
and
"have to" can use "do"

Am i right??

[Torsten]

Yes Lisa, you are right.
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary

[Tiffanyenglish]

Hi Torsten,

In test #7, I got 9 out 10 because I carelessly missed answering #8. Although I answered all of nine questions correctly, but I can't explain why. It sounded right to me. That's how I would normally speak. I would like to learn more about the modals. Please let know where I can learn more about it. I don't have a specific question but would like to know more about other modals. Thank you.

Tiffany

[Lanhuong]

Can you show me the differences between " must" and " have to"?
Thanks for your help!

[Torsten]

Sure, please read this: "must" vs "have to"

And this: use 'must or have to'

And this: Modal verbs: must/have to
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary