In this task, you are given a premise sentence, two possible options and a question word. If the question was cause you should select the option that is a possible cause of the premise sentence, and if the question word was effect you should find the option which is a possible effect of the premise sentence. Answer with "A" or "B".

The tenant misplaced his keys to his apartment. (A) His landlord unlocked the door. (B) His landlord repaired the door., Question: effect

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
A