Read the sentence.

Riding a bicycle to school can improve health and increase fitness.

Which fact would support the cause-and-effect relationship in the statement?

A study that followed certain people's health as they drove or rode in a car or bus to school and then switched to riding a bicycle. The study should monitor their health before the switch and then compare it to their health during and after starting to ride a bike.

Fitness tests could be given before and after too, to show how their level of fitness has changed by starting to ride the bike.