I was watching TV when I heard the glass break

[Sulaini]

English Grammar Tests, Elementary Level

ESL/EFL Test #235 "Various Conjunctions (3)", question 2

Neither one of the boys admitted to breaking the window. I didn't see who did it because I was watching TV ......... I heard the glass break.

(a) when
(b) if
(c) or
(d) since

English Grammar Tests, Elementary Level

ESL/EFL Test #235 "Various Conjunctions (3)", answer 2

Neither one of the boys admitted to breaking the window. I didn't see who did it because I was watching TV when I heard the glass break.

Correct answer: (a) when
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Please explain "the glass break" and not "broke". thanks

[Our Tort System]

Because with verbs of perception you must use a bare infinitive (or an -ing form)

Here's an in-depth explanation:
http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv214.shtml
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If it's not easy, don't do it!
That's how I got where I am.

[Sulaini]

Thanks for the explanation...really appreciate it.