Please answer! If you answer you get brainlist :D

A test variable is a user-defined, name-value pair that stores and refers to information throughout a test and between tests. For example, in a study looking at how tutoring impacts test scores, the dependent variable would be the participants' test scores, since that is what is being measured...

The control group is defined as the group in an experiment or study that does not receive treatment by the researchers and is then used as a benchmark to measure how the other tested subjects do. For example, The control group is used in an experiment as a way to ensure that your experiment actually works. Your experimental group would be given the Gatorade and your control group would be given regular water. The conditions must be exactly the same for all members of the experiment.

A limiting factor is anything that constrains a population's size and slows or stops it from growing. Some examples of limiting factors are biotic, like food, mates, and competition with other organisms for resources. Limiting factors are usually expressed as a lack of a particular resource.

Infectious agents commonly spread through the direct transfer of bacteria, viruses, or other germs from one person to another. This can happen when an individual with the bacterium or virus touches, kisses, or coughs or sneezes on someone who isn't infected.

Explanation:

colorless gas, exhibiting a blue glow when placed in an electric field

b) solid

its a type of rock