Difference between fill up and fill out

[clare]

Test No. incompl/advan-6 "Phrasal Verbs", question 1

If you want to join that club, you have to ......... a form and send it to your secretary.

(a) fill up
(b) fill out
(c) fill into
(d) fill over

Test No. incompl/advan-6 "Phrasal Verbs", answer 1

If you want to join that club, you have to fill out a form and send it to your secretary.

Correct answer: (b) fill out
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Difference between fill up and fill out

clare

[Alan]

I think fill up is better associated with quantities and liquids as in fill up your glass.
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English as a Second Language
You can read my ESL story Future

[Zheng.coral]

could you please explain the meaning of the other two phases, 'fill into' and 'fill over'? Thanks.