Meaning of idiom: "didn't bat an eyelid"

[Joe]

English Idioms and Expressions, Intermediate level

ESL/EFL Test #14 "British Idioms", question 9

Not really. Funny thing is I asked her out and she didn't bat an eyelid. What I want to know is whether I did the right thing.

(a) didn't answer me
(b) didn't look at me
(c) didn't help me
(d) didn't show any reaction

English Idioms and Expressions, Intermediate level

ESL/EFL Test #14 "British Idioms", answer 9

Not really. Funny thing is I asked her out and she didn't show any reaction. What I want to know is whether I did the right thing.

Correct answer: (d) didn't show any reaction

Your answer was: incorrect
Not really. Funny thing is I asked her out and she didn't answer me. What I want to know is whether I did the right thing.
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she didnt answer so that can also fall into she didnt show any reaction right?

JOE SOMEBODY

[Mister Micawber]

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Not really. Not to bat an eyelid is not to respond in any way whatsoever. Not to answer suggests merely the lack of a vocal response.

The question asks you for the definition of the idiom, not to bat an eyelid, which means not to show any reaction.
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Native English teacher at Mister Micawber's