Question

to be a possible answer to a scientific question, a hypothesis must be testable. unique. written. controlled.

Explanation:

In scientific inquiry, a hypothesis must be testable so that experiments or observations can be designed to determine its validity. It doesn't have to be unique as similar hypotheses can be proposed by different researchers, and while it may be written down, being written isn't a defining characteristic for it to be a valid hypothesis for a scientific question. Also, the concept of being "controlled" isn't relevant to what makes a hypothesis suitable for a scientific question.

Answer:

testable