difference between hard luck and bad luck

[Ildikos]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #57 "Lucky You", question 5

You really couldn't blame anyone for the accident because it was just a case of ......... luck.

(a) worse
(b) worst
(c) foul
(d) bad

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #57 "Lucky You", answer 5

You really couldn't blame anyone for the accident because it was just a case of bad luck.

Correct answer: (d) bad

Your answer was: correct
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Hello, would you please describe the difference between hard luck and bad luck? Could these expressions be interchangeable?
Thank you in advance!
Ildikos

[Conchita]

Yes, Ildikos, you could say the phrases 'hard luck' and 'bad luck' are interchangeable.