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. 

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