Why must an experiment or a survey be controlled? what is the difference between the control group and the experimental group in a controlled experiemnt?

Which of the following shows the correct order in which light information travels through the eye? (2 points) lens, pupil, retina, optic nerve pupil, lens, retina, optic nerve pupil, lens, optic nerve, retina lens, pupil, optic nerve, retina

The “ecological footprint” left by a citizen of a developed nation is about four times larger than that left by a citizen of a developing nation. why is this the case?

Draw the farm's ppf for corn and beef. draw a point that shows an inefficient combination of corn and beef. label ita. draw a point that shows an unattainable combination of corn and beef. label itb. draw a point that shows an efficient combination of corn and beef. label itc.