Which postulate explains why a tripod will not tip over?
a. a line contains at least two points.
b. a plane contains at least three noncollinear points.
c. space contains at least four noncoplanar points.
d. if two planes intersect, then their intersection is a line.

The correct answer is B. A plane contains at least three noncollinear points. What this means simply put is that the three legs touching the ground constitute a plane and is stable. If there were only 2 it could tip over easily. If there were 4 legs then one leg might not touch the ground and might hang in the air. This way, when there's three, all three will at all times touch the ground and will constitute a plane.

I think your initial answer was correct, no need in changing it