It would be D, fertilization.
Answer:
Experimental groups: type of dogs
Dependent variable: hearth rate
Independent variable: the amount of caffeine
Explanation:
The dependent variable is the variable being measured or tested in a given study, while the independent variable isn't changed by the other variables. In this case, the heart rate is dependent on the amount of caffeine, which is then the independent variable. The experimental groups are the groups exposed to the independent variable.
The first event or first thing they do, because the first thing they do is exercise for 2 hours everyday to keep their muscle and bone strength.
