Why must controls (such as plants given water only) be used in the fertilizer experiment described in the study guide?

Ronald wants to see if a new shower cleaner works better in removing soap than his old cleaner. he uses the new cleaner on one half of the shower tiles and his old cleaner on the other half. identify the independent and dependent variables in this experiment. enter your answer in the space provided.

If jane has the blood type ab and marries john who has type o blood what are the possible phenotypes of their first kid?

Which was most likely an effect on society that resulted from improvements in blood handling during world war i and world war ii?