Question

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

Explanation:

In the scientific method, a hypothesis (a proposed explanation for a scientific question) must be testable. This means it can be investigated through experiments or observations to determine if it's supported or refuted. A hypothesis doesn't need to be unique (multiple hypotheses can address a question), doesn't have to be written (though documentation is common, the key is testability), and "controlled" refers to experimental conditions, not a property of the hypothesis itself.

Answer:

A. testable