Set S is the prime integers between 0 and 40. If three numbers are chosen randomly from set S, what is the probability that the sum of these three numbers is odd? Choices:
A) 15/56
B) 3/8
C) 15/28
D) 5/8
E) 3/4
Total number of combinations=12C3=220................(1)   Total number of combinations including 2 and two other numbers=11C2=55......................(2)   Therefore the difference ie. (1)-(2) is the set of 3 primes without 2=(220-55)= 
<gadget id="calculator">(220-55)</gadget>
<output>165</output>
165   So, probability=165/220=3/4   3/4
<result>E</result>
Set S is the prime integers between 0 and 40. If three numbers are chosen randomly from set S, what is the probability that the sum of these three numbers is odd?