What happens in a controlled experiment?

Question

a. Everthing is allowed to vary between treatments.
b. The treatments differ in only one way.
c. All the experimental subjexcts are the same.
d. Only one experimental treatment is used.

Answer 1

Your vocabulary is a bit confusing but here goes.
a is definitly incorrect; b is also incorrect; c depends on what subject is are they the things being tested? If so it is correct. d is incorrect because you need to compare what you are testing with some other thing. Treatment????
May be this will help..
A controlled experiment is an experiment that contains only one experimental variable. An experimental variable is the thing being tested. Everything else in the experiment or all other variables, must be the same. These variables are also called the controlled variables. Keeping these variables the same allows the experimenter to show that it was the experimental variable that caused the results.

Problem: Is Raid the best insecticide on the market?

Make a Hypothesis: Raid is the best insecticide on the market. If used it will kill insects 30% faster then other insecticides. This educated guess was determine by the experimenter based on the research done prior to making this statement.

Develop a controlled experiment:
Spray 5 separate plates with equal amounts of different insecticides. Cover each one with the same type and size glass. Add equal amounts of the same type of insects to each glass. Place them side by side and time the results.

Answer 2

D----