Carefully vs. quietly

[NLO]

Test No. incompl/inter-89 "Adverbially Speaking", question 2

Please listen ......... because this is important.

(a) quietly
(b) quickly
(c) nicely
(d) carefully

Test No. incompl/inter-89 "Adverbially Speaking", answer 2

Please listen carefully because this is important.

Correct answer: (d) carefully

Your answer was: incorrect
Please listen quietly because this is important.
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Why word guietly doesn't fit in here?

[Alan]

It must be carefully because it is important. Is it really possible to listen quietly?
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English as a Second Language
You can read my ESL story Passive Voice