In the following code that uses recursion to find the factorial of a number, what is the base case?

```
private static int factorial(int n)
{
if (n == 0)
return 1;
else
return n * factorial(n - 1);
}
```

a. factorial(int n)
b. if (n == 0)
return 1;
c. else
return n * factorial(n - 1);
d. Cannot tell from this code

b. if (n == 0)
return 1;