Why must an experiment have a control group?

When new rock is added to an oceanic ridge, the magnetized strips on either side of the ridge are evidence of sea-floor spreading. this is because the rocks on the two sides of the ridge o are equal in width and in polarity are polar opposites oare magnetized vary in width but are equal in polarity

True or false multiple lane changes must be done individually going through the same procedures for each lane change

Which feature would you expect to find in a population in which sexual selection depends on male competition?