Omar wrote a hypothesis about batteries called dry cells.

if more dry cells are connected end to end, a light bulb will work longer because there is more energy available.

what are the variables in his hypothesis?

Below are the choices:

The independent variable is the number of dry cells, and the dependent variable is the length of time the bulb works.
The independent variable is the length of time the bulb works, and the dependent variable is the number of dry cells.
The independent variable is the number of dry cells, and the dependent variable is the amount of energy available.
The independent variable is the amount of energy available, and the dependent variable is the number of dry cells.

I think the answer is The independent variable is the number of dry cells, and the dependent variable is the amount of energy available.