What's the difference between "that" and "which"?

[Sevides]

Test No. errors/elem-4 "Present Tense", question 2

What is the name of that picture which you look at on the wall?

(a) is
(b) which
(c) look at

Test No. errors/elem-4 "Present Tense", answer 2

What is the name of that picture which you are looking at on the wall?

Correct entry: are looking at
The error was: (c) look at

You have not found the error.
What is the name of that picture that you look at on the wall?
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Hi,
also that must be used instead of which isn't it?

[Alan]

Hi Sevide,

Which is all right here and avoids the repetition of the word that.

Alan
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English as a Second Language
You can read my ESL story Phrasal Verbs/bring