When do you use something and when do you use anything?

[El Ninjo]

English Language Tests, Intermediate level

ESL/EFL Test #147 "Compound words: someone, anyone, somewhere", question 7

What would you like to eat for lunch? .......... I don't mind.

(a) Nothing
(b) Something
(c) Everything
(d) Anything

English Language Tests, Intermediate level

ESL/EFL Test #147 "Compound words: someone, anyone, somewhere", answer 7

What would you like to eat for lunch? Anything. I don't mind.

Correct answer: (d) Anything
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Why is the answer anything? Can you give an explanation as to why we can't say something? When do you use something and when do you use anything? What is the difference in meaning and useage?

El Ninjo

[Mister Micawber]

.
In this sort of situation, we use 'something' when the speaker has a particular thing or things in mind and 'anything' when the speaker is thinking of no particular thing. A clue to the answer choice is in the added 'I don't mind' = 'I don't care [what I eat]'.

When asked what one would like to eat, 'something' is socially unacceptable because it conceals the answer to the question.
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_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber