John has 6 friends who want to ride in his new car that can accommodate only 5 people at a time (John plus 4 passengers). How many different combinations of 4 passengers can be formed from John's 6 friends?  Select the correct option
A) 3
B) 8
C) 10
D) 15
E) 20
6C4 = 15   The answer is 15.
<result>D</result>
John has 6 friends who want to ride in his new car that can accommodate only 5 people at a time (John plus 4 passengers). How many different combinations of 4 passengers can be formed from John's 6 friends?