What does this phrase mean: one fine day? Does it mean "in the end"?

[Kapil]

Test No. express/inter-4 "Picking you up", question 9

One fine day I expect everything will be clear to you.

(a) On a summer's day
(b) When the sun shines
(c) In the end
(d) Very soon

Test No. express/inter-4 "Picking you up", answer 9

In the end I expect everything will be clear to you.

Correct answer: (c) In the end
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I am confuse with option (a) & (c), please clarify this point

[Alan]

Hi kapil,

This idiomatic expression means at some time in the future but we don't know when. On a summer's day means simply one day in the summer and isn't idiomatic.

Alan
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English as a Second Language
You can read my ESL story Present Simple