Meaning of shrink to think

Test No. [color=blue]incompl/elem-31 “Responses (4)”, question 1

Mike: ‘Do you know what I did last night?’
Jane: ‘

(a) I shrink to think.
(b) I don’t think.
(c) I will not think.
(d) I do not think.

Test No. [color=blue]incompl/elem-31 “Responses (4)”, answer 1

Mike: ‘Do you know what I did last night?’
Jane: ‘I shrink to think.

Correct answer: (a) I shrink to think.
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Does it mean that she doesn’t want to know what he did last night? Or that she is thinking very hard about what he could have done?

This is a semi humorous/sarcastic remark that means she hesitates to think in case it’s something she doesn’t want to know about.

more explanation please