Aresearcher studied two groups of fruit flies
population a was kept in a 0.5 l container
population b was kept in a 1 l container
3. the independent variable in the controlled experiment was the
a. number of flies
b. number of groups studied
c. number of days
d. size of the containers

D

Explanation:

An independent variable is variable  in an experiment that is not affected by another variable and is often used to influence the other variables, which are dependent variables. In this case the size of the container is the independent variable because its changes affect the behavior of the fruit flies. The behavior of the fruit flies is the dependent variable. The number of flies, that is kept constant, is the controlled variable.

answer; the correct answer is (beta)

"a.) well–developed vascular system."