What does "go to the foot of my stairs" mean?

[Mara]

Business Idiom in English, Intermediate level

ESL/EFL Test #136 "How to make exclamations", question 10

I'll go to the foot of my stairs! It must be at ......... 20 years since we last met.

(a) last
(b) length
(c) least
(d) end

Business Idiom in English, Intermediate level

ESL/EFL Test #136 "How to make exclamations", answer 10

I'll go to the foot of my stairs! It must be at least 20 years since we last met.

Correct answer: (c) least

Your answer was: ?
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" go to the foot of my stairs"- what does it mean?

[Alan]

Hi,

This is an expression showing great surprise. It suggests that you really can't believe what you hear.

Alan
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English as a Second Language
You can read my ESL story Conditionals