Difference between appetite and craving

[Rich7]

Test No. incompl/advan-81 "GMAT Verbal Quiz (4)", question 7

They say that pregnant women develop a ......... for certain foods and must eat them all the time.

(a) appetite
(b) craving
(c) thirst
(d) eating

Test No. incompl/advan-81 "GMAT Verbal Quiz (4)", answer 7

They say that pregnant women develop a craving for certain foods and must eat them all the time.

Correct answer: (b) craving

Your answer was: incorrect
They say that pregnant women develop a appetite for certain foods and must eat them all the time.
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Can or can we not develop an appetite for any kind of food?

[Alan]

Yes, you can acquire/develop an appetite for certain food but I deliberately added in the sentence must eat them all the time to indicate that this was a craving and so much stronger than appetite.
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[Rich7]

Plus the fact that you put the indefinite article "a" hence one should pick "craving" otherwise It wouldn't be correct.