The Number of Ways to Choose K Out of N

Multiple Choice

The number of ways to choose k out of n things is ______.

A) the number of ways to choose k - 1 out of n - 1 things
B) the number of ways to choose k out of n - 1 things
C) the sum of the number of ways to choose k - 1 out of n - 1 things and the number of ways to choose k out of n - 1 things
D) the product of the number of ways to choose k - 1 out of n - 1 things and the number of ways to choose k out of n - 1 things