Answer:
C) non-negative
Explanation:
A) cannot be true, as normally we have distances between points that are not identical. and such a distance cannot be 0.
B) means everything larger than 0. but that is not true, because sometimes we have to deal with identical points. and that distance between identical points is 0.
D) a distance can never be negative. what would that mean ? simply impossible. but note: a directed movement can be negative (like moving c units away from something). but the moved distance itself is not negative.