Answer:
Hypothesis.
Step-by-step explanation:
A hypothesis is a testable explanation for an event. For example, if you see a certain type of bird at your bird feeder, but never your neighbor's, you could come up with the hypothesis that that specific species of bird likes something that is present in your own birdseed, but not your neighbor's. This is easily testable by switching out different birdseeds and seeing which ones attract the birds, and serves to explain why the birds only appear at your bird feeder.