What makes an inactive question to appear in active list? The question asked in 2015/8/10 and has 2 answers (one accepted). There is no recent comment, answer, edition, and other activities.
In this case, there was an answer posted earlier today, and shortly after deleted by the author. For users below 10k reputation, such activities are invisible, but users with at least 10k can see it.
Generally, sometimes inactive questions are bumped by the community bot, which also can bring actually inactive questions to the front page or the "active" tab.