A survey claims that 9 out of 10 doctors (i.e., 90%) recommend brand A for their patients who have children. To test this claim against the alternative that the actual proportion of doctors who recommend brand A is less than 90%, a random sample of 100 doctors results in 83 who indicate that they recommend brand A. The value of the test statistic z in this problem is approximately:
a. z=-1.99
b. z=-1.83
c. z=2.33
d. z=-2.33