Felisha wants to determine if the amount of time stretching allows gymnast to do a back flips
correctly. she has 5 students stretch for zero minutes, another 5 students stretch for 5 minutes
and the other 5 students the normal stretching time of 15 minutes. can you determine the
independent variable, dependent variable, control, and 2 constants in this experiment?

An independent variable can be described as a variable which is changed in a scientific experiment to determine its effect on the dependent variable. In the following experiment amount of the time stretching is the independent variable.

A dependent variable can be described as the variable which depends on other factors. In the following experiment, back flips are the dependent variable.

A control experiment is the experiment which is used to compare the experimental groups. In the following experiment, five students which stretch for zero minutes is the control group.

A constant is the part that doesn't change in the experiment. In the following experiment the number of students  and the type of exercise or gymnast remains constant.

answer: - b cells

explanation: -

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.

substitution is the answer in this case