Constants ("controlled variables") and a control are easily confused by
students! How would you explain the
difference between the two words?

Please find the explanation below

Explanation:

The control variable of an experiment or constant are variables that the experimenter keeps constant or unchanged for all the groups throughout the experiment. The constant can influence the result of the experiment if not kept unchanged.

On the other hand, a control group is a group that does not receive any experimental treatment in order to compare the effect of the independent variable on the dependent variable. The control group receives every other thing including the constants, with the exception of the independent variable.

In a nutshell, the control group is used as a standard comparison for the experiment performed i.e. compare what will happen if an independent variable is changed in the experimental group while the control variable is simply a factor that must be kept constant throughout the experiment to avoid alterations.

the answer is "a.) well–developed vascular system."

explanation:

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.