单选题：In the following function, what is the ending condition of recur

In the following function, what is the ending condition of recursive programming?
```
int xFunction(int n)
{
if (n == 1) return 1;
else return n + xFunction(n - 1);
}
```



A.n is 1.
B.n is greater than 1.
C.n is less than 1.
D.no base case.


答案：A