1. Direct-jump from bat population
2. Started in bats, came to humans through intermediate animal
3. Came from frozen food outside of China
4. Lab accident.
I used to think the lab accident theory was crazy, because it sounds like a science fiction movie. Not an impossible theory, just a crazy one.
But according to this article, despite a year of investigation, (1) is unlikely because we haven't found anyone that interacted with the nearest bat population hundred of miles away that didn't work in the virus lab in Wuhan and that caught the virus, (2) is unlikely because we would have found the intermediate animal by now, (3) is unlikely because the first case found was in China (and not somewhere else... if frozen food had the virus, the food would have had it before it was frozen, and someone else would have had it), and (4) is unlikely because a government famous for blocking information and is paranoid about how it is perceived domestically and internationally says "No, trust us on this one."
At some point, crazy theories become the most likely. Hopefully I'm wrong though, and they find an explanation that isn't "lab accident." It seems like we should be studying viruses and sharing that information with each other, and accidents like this will make it more likely that such research doesn't happen.