The correct option is D but
The given sentence needs to be filled with the most suitable conjunction. This sentence has two contrasting clauses, as the first clause says that the person went to buy a CD and the second clause says that he didn't get it. Hence the correct option is B - 'I went to buy a CD, but the shop did not have what I was looking for', 'but' is always used to join two contrasting clauses. Option A is incorrect, as 'and' is used to combine two equal clauses, Option C is incorrect, as 'so' is used to join the main clause with a dependent clause of reason. Option D is incorrect, as 'or' is used to join two alternative clauses.