Scientific investigations begin by asking questions that can be tested, measured, or both. which question meets this criterion?

The answer choices are not provided, so I cannot select the correct one. However, I may provide you examples and guidance on how to choose the correct one.
As mentioned in the explanation, a scientific question must have a variable that is changed, the independent variable, and a variable on which the effect of the change is measured. This is the dependent variable. Examples of such questions include:

How will the amount of water given to a plant affect its rate of growth?
What will be the amount of sugar that can be dissolved in water at a given temperature?
At what temperature will a balloon filled with air pop?

All of these questions may be tested using experiments.

The answer is constant.