What's the simple past form of 'must'?

[Neyl]

Test No. incompl/elem-7 "Modals", question 1

I ......... go to see the doctor last week because I was very ill.

(a) must
(b) must to
(c) had to

Test No. incompl/elem-7 "Modals", answer 1

I had to go to see the doctor last week because I was very ill.

Correct answer: (c) had to

Your answer was: incorrect
I must go to see the doctor last week because I was very ill.
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I must go to see the doctor last week because I was very ill.

Neyl

[Torsten]

Must doesn't have a simple past form, that's why you have to use had to instead.
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary

[Kharisma]

So, we can't use might as a simple past form of must, can we? Because I've heard somebody use it... Please give me the answer...
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Thanks for sharing

[Conchita]

[Kharisma]

O, iya... i see... thank you very much! ^_^
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Thanks for sharing