Prepositions before nouns?

[Howiy]

English Language Tests, Intermediate level

ESL/EFL Test #99 "Student Teacher Dialogue (2)", question 2

Student: Well I know that they usually come ......... a noun.

(a) on
(b) before
(c) after
(d) under

English Language Tests, Intermediate level

ESL/EFL Test #99 "Student Teacher Dialogue (2)", answer 2

Student: Well I know that they usually come before a noun.

Correct answer: (b) before

Your answer was: incorrect
Student: Well I know that they usually come after a noun.
_________________________

why before

[Beeesneees]

You have to look at the previous test question as the questions are all linked.

The previous question was 'what do you know about prepositions'?
Prepositions usually come before a noun, not after it.
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Cheers m' dears!