Ralph wants to estimate the percentage of coworkers that use the company's healthcare. He asks a randomly selected group of 200 coworkers whether or not they use the company's healthcare. What is the parameter?

a.the percentage of surveyed coworkers that use the company's healthcare

b.the 200 coworkers surveyed

c.specific "yes" or "no" responses to the survey

d.all coworkers that use the company's healthcare

e.the percentage of all coworkers that use the company's healthcare