Question

what characteristic is necessary for a hypothesis to be useful in a scientific investigation?
it must happen in a lab.
it must be true.
it must be testable.
it must be proven.

Explanation:

A hypothesis in scientific investigation needs to be testable so that experiments can be designed to support or refute it. It doesn't have to occur in a lab, be true from the start, or already be proven.

Answer:

It must be testable.