I haven’t worked as a mechanic before, ________ I’ve been fixing cars since I…

Answer:

yet

Explanation:

Always is an adverb of frequency, like never, often, frequently, and usually.

Yet is a conjunction meaning nevertheless or however. Yet usually carries a sense of negation, so and yet means the same thing as but still.

No longer means not now as formerly; not any more.

We use already to show that something has happened sooner than it was expected to happen.

Therefore, “yet” is the most appropriate choice here.

Option (B) is correct.