Answer: Yes, it is a function.
Explanation:
This question is:
"A relation between time and distance traveled by a biker is a function?"
Well, as you may know, a function is a relation where each value in the domain or input, has only linked one value in the range or output.
In this relation the domain is time and the range is the distance.
Now, as you know, at each given time, the distance of the biker can be only one (he can not be at different locations at the same time) so this relation is actually a function.