at a discount

[English Learner]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #693 "Prepositional Phrases - At, By, For and To (4)", question 2

I got that sweater ......... a discount last week because I used a coupon I got in the mail.

(a) at
(b) for
(c) by
(d) to

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #693 "Prepositional Phrases - At, By, For and To (4)", answer 2

I got that sweater at a discount last week because I used a coupon I got in the mail.

Correct answer: (a) at

Your answer was: incorrect
I got that sweater by a discount last week because I used a coupon I got in the mail.
_________________________

What is the used of at? by? for? to?

[Beeesneees]

You can find the meanings , uses and examples of usage of those words here:
Learner's Dictionary

If you have further, more specific questions after you have checked the dictionary, please ask again.
_________________
Cheers m' dears!