Through any three noncollinear points, there is exactly one plane containing them. points w, x, and y are noncollinear.

Correct!

When thinking of what determines a plane we can make the following comparison.

If a plane was the top part of a table, 3 legs, whose tops are points W, X and Y may hold it, as shown in the first picture.

but if the legs are in a line, as in the second figure, they may not hold the top part, so 3 collinear points cannot determine a plane. 

Sorry can't answer that question

In all honesty, there really is no “work” per say to show. mainly it’s just using the process of elimination. the question is asking which domain(s) would be the most appropriate for the function c(n). n is the number of observed vehicles so right away, 1, 2, and 3 can be eliminated.why? 1, 2 start in the negatives and therefore it is impossible to observe negative cars. so, #4 would be the best answer to the given problem.