Answer: Wet or dry environment.
Step-by-step explanation:
The independent variable is the variable that a researcher manipulates in an experiment in order to carry out a study on the incidence of the expression of the dependent variable. Therefore, the independent variable is the one that changes or is controlled to see its effects on the dependent variable.
Researchers can then design a container with a wet or dry environment. But it's the pillbugs that are going to choose where to go and how long to spend in each part. So the time they spend in each part is a dependent variable since that cannot be controlled by the scientists conducting the experiment. Henceforth, the researches will just record this dependent variable without controlling it. But they can decide what to put in the container to make it wet or dry environment, or whatever they want to design. So wet or dry environment is the independent variable.