Difference between stale and rotten

[sandra]

Test No. incompl/inter-36 "Go for it", question 6

I'm afraid you've left that food too long out of the fridge and now it's ..........

(a) become flat
(b) become rotten
(c) become rich
(d) become stale

Test No. incompl/inter-36 "Go for it", answer 6

I'm afraid you've left that food too long out of the fridge and now it's become rotten.

Correct answer: (b) become rotten

Your answer was: incorrect
I'm afraid you've left that food too long out of the fridge and now it's become stale.
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Why we couldn't use "stale" to describe the food is gone off?Thank you!

[Alan]

Stale doesn't really work here because it means the opposite of fresh and food can become stale by simply leaving it exposed to the air so that it becomes dry and unpalatable. It is an adjective that can apply to foodstuffs in general. Rotten on the other hand is needed here because this food has apparently to be kept in a fridge until used and if it is left out of the fridge, it starts to decompose and become rotten. Rotten can also refer to something like wood that has become damp and is now falling to pieces. You might also note the figurative use of both these adjectives: stale can refer to a literary work or piece of writing that has no original content. Rotten can mean awful/terrible/horribe as in: rotten weather/rotten luck.
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