The code below is supposed to add the numbers from 1 up to and including 10. It does not calculate the correct sum. The problem is caused by a(n) ________ error.

```
int sum = 0;
for (int count = 1; count < 10; count++)
sum += count;
```


a) syntax
b) compilation
c) requirement
d) off-by-one
e) testing

e) testing