The angle measures 30°, 60°, 120°, and 150° are written on
slips of paper. One student chooses a slip, identifies the
type of angle, and returns the slip. A second student
chooses a slip. What is the probability that the second slip
will contain an obtuse angle measure, given the first slip
contained an acute angle measure?

A. 1/16
B. Not here
C. 1/2
D. 1/4