The answer is: There is no error.
Complex sentences consist of a subordinate or dependent clause, which is introduced by a subordinating conjunction like <em>even though</em>, and an independent clause, which can stand on its own. They can be separated by a comma.
In the example sentence, the subordinate clause is:
Even though I had no previous experience,
Finally, the independent clause is:
I enjoyed painting the living room with my friends.
The rest of the alternatives are incorrect because the clauses are separated or do not express the same meaning as the original sentence.
