Difference between surely and certainly

[Arielfrommendoza]

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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Hello everybody!!!
I have just started with the tests.
In this one I can?t get the difference between certainly and surely. Would you help me please?

[Alan]

In this context surely is when you believe that's what the other person wants/believes but certainly is to show that this is what you believe/want.

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English as a Second Language
You can read my ESL story Phrasal Verbs/look