In the following pseudocode which uses recursion to find the factorial of a number, which is the base case? Module main() Declare Integer number Declare Integer numFactor Display "Enter a non-negative integer:" Input number Set numFactor = factor(number) Display "The factorial of ", number, " is ", numFactor End Module Function Integer factor(Integer n) If n == 0 Then Return 1 Else Return n * factor(n - 1) End If End Function