What is the independent variable? Select one option from the list below.

1 is the correct answer help me please .thanks

Sue is setting up an experiment to test whether fly maggots select a dark or a brightly lit environment. She sets up a chamber in which there is a gradient in light intensity from one end (dark) to the other (brightly lit).
The experimental hypothesis was
“There will be a large difference between the number of maggots in a dark environment and the number in a brightly illuminated one.”
What is the independent variable? Select one option from the list below.
1) Light intensity

2) The reaction rate of maggots

3) The average number of maggots in each light condition

4) The total number of maggots

5) The number of maggots in each light condition

6) The distance between the darkest and most brightly lit parts of the choice chamber

7) The time of day

The independent variable in this experiment is the factors that the researcher deliberately manipulates, which in this case is the light intensity. Therefore, option 1) Light intensity is the correct answer.