Let C = {p, l, u, s}. How many proper subsets does C have?

Proper subsets are all subsets except C itself.

16

To determine the number of proper subsets that a set has, we can use the formula 2^n - 1, where n is the number of elements in the set.

In this case, C has 4 elements: p, l, u, s.

Using the formula, we can calculate the number of proper subsets:

2^4 - 1 = 16 - 1 = 15

Therefore, C has 15 proper subsets.