Some questions have multiple answers which are all high quality and give different insight into what's being asked. For example Why would security cover things like natural disasters? I'm not sure how to, or if I should, pick the accepted answer, since in a sense there isn't one correct answer. What should be done?
Remember the wiki:
Accepting an answer is not meant to be a definitive and final statement indicating that the question has now been answered perfectly. It simply means that the author received an answer that worked for him or her personally.
The accepted answer does not imply a correct answer. It only states that the answer was (most) useful to you (the person who asked the question). When the accepted answer does not look as the most complete answer, I can see two main ways of understanding why a certain answer is the accepted one:
The answer did help the OP directly, even if it guessed the actual problem OP had rather than the one described in the question.
It is the answer that best described the problem and solution to OP. Different people understand things in different ways and have distinct technical knowledge. OP may prefer the simple answer to the complete one.
The list is by no means exhaustive. But the point I'm trying to make is that you can use your subjectivity to evaluate the answer to accept.
You can still upvote all answers that you consider to be good answers.
In addition to @grochmal's answer, if 2 answers only give half the answer each but together provide a full solution, an alternative is to simply create a new answer, collating the best from each answer, in order to provide a single answer with a full and complete solution.
Yes, this is allowed, and sometimes even recommended.
You could look at this a different way, and conclude that the question was too broad because multiple different answers satisfied it. Consider editing the question to narrow the focus down to one "most" appropriate answer, and then ask a new question in a slightly different way that would elicit one of the other appropriate answers.