Answer – C. the sample size 16 is too small
If we toss a coin 16 times in order to test the hypothesis H0: p = 0.5 that the coin is balanced, we can't use the z-test for a proportion in the situations because the sample size 16 is too small. The z-test is best used when the sample size is greater than 30; when the sample size is less than 30, t-test is more appropriate.