Answer: d. The graph will be discrete because there is no such thing as a partial person to sign up and the booth is set up once each day for sign ups.
Explanation:
A Discrete variable is one that can be determined with absolute certainty because it takes on a particular value. This is unlike a Continuous variable that can take up an infinite value within a data set.
As the number of humans can be determined with certainty because there is no such thing as a partial human and also because the booth will be set up once each day, the graph will have to be Discrete in nature.