Question

what is always included in a comparative investigation? a dependent variable an independent variable a hypothesis a scientific question

Explanation:

In a comparative investigation, we compare groups to see how the independent variable (the one we manipulate or that differs between groups) affects outcomes. So an independent variable is always included to make the comparison. A dependent variable is what's measured, a hypothesis is a prediction, and a scientific question is the inquiry—none are as essential for the comparison as the independent variable.

Answer:

an independent variable