<span>Whatever the focus of the experiment is, plus any others factors that might influence the outcome of the experiment. If you are testing a new cancer drug, the experimental group and the control group must both be people with the same type of cancer, and both be a representative distribution of the population, all races, genders, ages, etc. You want the only difference in the two groups to be what you are studying, i.e. the effects of the drug.</span>
Answer:
I think is 2.
Explanation:
(The entire range of wavelengths or frequencies of electromagnetic radiation extending from gamma rays to the longest radio waves and including visible light)
<em><u>This</u></em><em><u> </u></em><em><u>it</u></em><em><u> </u></em><em><u>you</u></em><em><u> </u></em><em><u>can</u></em><em><u> </u></em><em><u>do</u></em><em><u> </u></em><em><u>it</u></em><em><u> </u></em><em><u>boy</u></em><em><u> </u></em><em><u>or</u></em><em><u> </u></em><em><u>girl</u></em><em><u> </u></em>
Solar energy - A
nuclear energy - B
fossil fuel energy - C
wind energy - D
geothermal energy - E
<span>The Appalachian Mountains were formed when colliding tectonic plates folded and upthrust, mainly during the Permian Period and again in the Cretaceous Period. The folds and thrusts were then eroded and carved by wind, streams and glaciers. These erosive processes are ongoing, and the topography of the Appalachian Mountains continue to change. They have changed with the miles of land that are cleared of all vegetation and topsoil. In the 1970's coal miners literally blow away the top of a mountain to get to the coal underneath.</span>