That 100-year timeframe is just for the ones we know about. It’s the one we don’t see coming that will be the problem. A long-period asteroid (one that hasn;t passed by before, at least in recorded history) might only be detected a couple of weeks out, which is not enough time to do anything with the technology we currently have. A long-period comet wouldn’t be much better.
More quarters!!!!
My fingers are getting tired....