When cody arrived at the gym, it was relatively empty. she started riding a stationary bike at a leisurely pace. once a few other people sat down at nearby bikes, she began to speed up her pace and push herself a bit more. what is this phenomenon called?

This phenomenon is called social facilitation.

Explanation:

Social facilitation refers to one's tendency to improve his/her performance when other individuals are present. When the individual is alone, he/she has certain performance but having other individuals around tends to make this individual want to improve.

In this case, Cody is riding the bike at a leisurely pace but as soon as the gym gets less empty, she improves her performance by the sheer presence of others.

yes. it has been proven significantly, especially with a more than ever huge influence of social media & everybody's opinion. for example, we could bring up movements such as the black live's matter movement, or something as such as the march for our lives movement. more than ever it seems as though everybody is starting to care more about this world.

the answer is d.index