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

[Admira]

hi Torsten
i just finished exercise modal verbs i have scored 10 out 10 after i repeated once
i wasn't clear about this sentence;
I COULD HAVE BOUGHT THAT CAR BUT I DIDN'T HAVE ENOUGH MONEY TO PAY FOR THE PETROL,
my answer was HAD,because the verb had it's past tense ,and you have used modal verb could (past tense) that's way i was sure had was the right answer,it will be great if you give me some examples to clear me out please.
,you have asked me if i know what are modal verbs?
to be honest i didn't knew it,i search and i find out what are they.
modal verbs are helper verbs that are used to change the grammatical mood of a sentence.they are; can may will shall in present tense,and ;should would might could must in past tense
thank you for every lesson you have sended to me,it's great to learn English and great to learn grammar too
yours sincerely admira

[Hamidullah]

Dear teacher,
I have much problem using "of" in the sentences i only know that "of" the possession of something or someone but it dose not give me complete sense.

[Mehraban]

OK
I think it was not a simple test. Or better to say it was not a simple test for me. my score is 7 from 10. I will repeat it next time.

[Lal]

Sir
Could you tell me whether the followiing sentences are correct or wrong?
1) What I wanted to know is ------.
2) What I wanted to know was------
My question is in the above uncompleted statements - the part of 'be' should be past or present.
Thank you.
Lal

[Mitra584]

Dear Torsten
I have answered 10 questions out of 10 correctly
about MODAL VERBS
regards
Mitra

[Tree0211]

Dear Mr.Torsten
And good afternoon everyone.
I feel very exciting when i read all of your comments in this site. It's useful for me to know more about "must and have to" and other interesting things.
I'm looking forward to receiving next lesson.