Meaning of "It was the least I could do"

[Elif I]

English Grammar Tests, Elementary Level

ESL/EFL Test #33 "Responses (6)", question 6

John: 'I must say you really helped us out when we lost those passports.'
Sue: '.........

(a) It was the least I could do.
(b) I couldn't do more.
(c) I couldn't do less.
(d) I couldn't do least.

English Grammar Tests, Elementary Level

ESL/EFL Test #33 "Responses (6)", answer 6

John: 'I must say you really helped us out when we lost those passports.'
Sue: 'It was the least I could do.

Correct answer: (a) It was the least I could do.

Your answer was: incorrect
John: 'I must say you really helped us out when we lost those passports.'
Sue: 'I couldn't do more.
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i don't understand the meaning of "It was the least I could do"
thanks for explanation

Elif

[Alan]

Hi Elif,

That was the least I could do means I had to do something and what I did was really very small.

Alan
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English as a Second Language
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