Done my piece vs. done my bit

[Bitty]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #559 "English Slang Idioms (197)", question 7

"We are not ready to present our findings to the committee yet. We still need to conduct some more tests to verify the validity of our work even more. I have done my ......... and have spoken to the head of the chemistry department to have arrange for an independent chemist to review our work. Please talk amongst yourselves while I answer this call to see what else we can do," Linus said to the team.

(a) piece
(b) homework
(c) action
(d) bit

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #559 "English Slang Idioms (197)", answer 7

"We are not ready to present our findings to the committee yet. We still need to conduct some more tests to verify the validity of our work even more. I have done my bit and have spoken to the head of the chemistry department to have arrange for an independent chemist to review our work. Please talk amongst yourselves while I answer this call to see what else we can do," Linus said to the team.

Correct answer: (d) bit
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why not piece here.elaborate please

[Mister Micawber]

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The idiom is 'do one's bit' = do one's share or part of an effort.
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Native English teacher at Mister Micawber's

[MrPedantic]

There seems to be typo in that one – "have arrange".

"To verify the validity of X even more" doesn't sound quite right; you can verify the validity of X, or you can't.

Also, "I've done my bit" would usually signal that you had done all that was required of you; but that does not accord with the context.

I wonder too why "homework" wouldn't be a suitable answer.

(Sorry to be critical; but as Linus has discovered, peer review is sometimes an advantageous discomfort.)

Best wishes,

MrP

[Mister Micawber]

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Thanks, MrP. I tried to get to it earlier, but it is out of my reach. Someone will clean it up soon.
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Native English teacher at Mister Micawber's