Sports such as soccer, basketball, squash and tennis may also may improve his cardiovascular fitness. He should also try to intensify and work out more frequent if he wants to improve.
Answer: Having the most offsprings
Explanation:
Natural selection is the differential survival and reproduction of the some of the members of the population those who have benefit of survival under the adverse conditions.
Such members of the population will survival and reproduce more offsprings than others this can be considered as fitness or survival of the fittest.
In a study, the independent variable is the thing that you change to see how the change produces different results. In this study, the independent variable would be the use of nicotine.
