Expression: You are quick to act, to seize an opportunity

[Kasia*]

English Idioms and Expressions, Intermediate level

ESL/EFL Test #11 "Home Sweet Home", question 10

I can see there are no flies on you but you must admit it is very cheap.

(a) you're not clear
(b) you're not easy
(c) you're not clever
(d) you're not stupid

English Idioms and Expressions, Intermediate level

ESL/EFL Test #11 "Home Sweet Home", answer 10

I can see you're not stupid but you must admit it is very cheap.

Correct answer: (d) you're not stupid
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Hi! I got confused with this one . I've heard the expression before - it meant "You are quick to act, to seize an opportunity". I understand it also means being "quick" mentally (=not stupid). Which one of these meanings is more common?

[Mister Micawber]

"quick" mentally
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Native English teacher at Mister Micawber's

[Kasia*]

Thanks!

[Tom]

[Kasia*]

Thanks for the link Tom. The explaination is great, although it doesn't mention the "you're not stupid" meaning of this idiom
(Or maybe it does? There is by all means nothing stupid in having a casual conversation with attractive young lady )