Our friend the Wendy the Waffle-Man has recently started a website for her waffle business, but she has two designs in mind for it. She wishes to conduct an experiment to determine which version of her website will influence waffle customers to buy more waffles. For simplicity, call these two versions "Version A" and "Version B". As visitors arrive to the website in real-time, 50% of the visitors to the website are randomly assigned to version A and 50% are randomly assigned to version B. Visitors do not know which version of the website they are seeing, though Wendy does, of course. After a month passes, Wendy will conduct her analysis. Over 6750 unique visitors visited the website in this time.
What are the response and explanatory variables for this experiment?

a. There is one explanatory variable, whether the visitor buys waffles or not. There is one response variable, the website version.
b. There are 2 explanatory variables, whether the visitor buys waffles or not. There is one response variable, the website version.
c. There are 2 explanatory variables, version A and version B of the website. There is one response variable, whether the visitor buys waffles or not.
d. There is one explanatory variable, the website version. There is one response variable, whether or not the visitor buys waffles.