Which of the following statements best describes a controlled experiment? a it tests the effect of a single independent variable b it avoids the use of variables c it shows the effect of a dependent variable on an independent variable d it eliminated the need for dependent variables

a. it tests the effect of a single independent variable.

Explanation:

This is the best definition of a controlled experiment. A controlled experiment is a scientific test that tests the effect of a single independent variable at a time. This variable is usually adjusted to see its effects on the system that is being studied. Moreover, a scientist performing this kind of experiment has to hold the variable constant to minimize or stabilize its effects.

A: It tests the effect of a single independent variable.

Explanation:

answer; i believe the answer is (polygenic inheritance;

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus