Consider the following algo:
while(1)
{
printf("...");
}
Without any input, it gives output. So, zero input and one output.
Also, consider given code segment:
int a;
while(1)
{
scanf(a);
if( a == 0)
print(a);
}
So, it can have zero or more output and can have one or more input.
So, answer is (C).