The correct option is B and
Option B: 'And' connects two words or clauses. Here, it connects the words 'years' and 'years'. The phrase 'years and years ago' is a set phrase. It emphasizes on how many years ago.
Hence option B is correct.
Option A: 'But' expresses contrast.
Option C: 'Or' refers to alternatives.
Option D: 'Since' refers to time or reason.
These conjunctions have specific functions, whereas the words 'years' and 'years' are simply to be connected. These words do not express contrast, alternatives or reason.
Hence options A, C and D are incorrect.