Surely vs. certainly

[KYTTIE]

Test No. incompl/elem-24 "Shopping", question 2

......... you must know what we need?

(a) Certainly
(b) Surely
(c) Definitely
(d) Absolutely

Test No. incompl/elem-24 "Shopping", answer 2

Surely you must know what we need?

Correct answer: (b) Surely

Your answer was: incorrect
Certainly you must know what we need?
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Hi Alan,
What's the difference between "absolutely, surely, definetely, certainly" in this sentence? I'm not convinced with the correct answer.
Thank you

[Alan]

You need this adverb because the implication is that the speaker is absolutely convinced that the other person must know. It's as if they are saying: Reassure me and tell me that you do know.
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English as a Second Language
You can read my ESL story A day in the life of a driving instructor

[Bashar]

Dear Alan

Can you give a sample for each?

[Alan]

Hi Bashar,

You asked