a scientist used a unique two - color code to identify each of the test subjects involved in a certain study . if the scientist found that choosing from among 5 colors produced enough color codes to identify all but 6 of the test subjects , how many test subjects were in the study ? ( assume that the order of the colors in the codes does not matter . ) Pick one.
A) 14
B) 15
C) 16
D) 17
E) 18

Rationale: 5 c 2 = 10 the number of test subjects is 10 + 6 = 16 the answer is c .
Answer: C