I am confused with BUT and OR

[Elka]

English Grammar Tests, Elementary Level

ESL/EFL Test #104 "Conjunctions: and, but, or & so", question 3

Have you seen ......... heard the latest musical by Andrew Lloyd Webber?

(a) but
(b) so
(c) or

English Grammar Tests, Elementary Level

ESL/EFL Test #104 "Conjunctions: and, but, or & so", answer 3

Have you seen or heard the latest musical by Andrew Lloyd Webber?

Correct answer: (c) or
_________________________

I am confused with but and or

Elka

[Pamela]

Here it's the kind of alternatve question giving a choice seen or heard. But according to the context cannot be used instead.
If we have changed the sentence by adding negative particle not but would have been the proper variant
Ex.Have you seen but not heard the latest musical by Andrew Lloyd Webber?
Here comes to mind that a fact that interests a person who is asking a question is Have he seen BUT not HEARD the latest musical by Andrew Lloyd Webber?