In a test of ESP (Extrasensory perception), the experimenter looks at cards that are hidden from the subject. Each deck of 60 cards contains equal numbers of cards with a star, a circle, a wavy line, or a square. An experimenter looks at each of the 60 cards in turn, and the subject tries to read the experimenter's mind and name the shape on each. What is the standard deviation of the number of correct responses if the subject does not have ESP?

A. 15

B. 5.25

C. 3.35

D. 1.33