Answer: Choice D) Plane PQY
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Step-by-step explanation:
By definition, a plane is formed by 3 non-collinear points. The three points cannot all be on the same line. If you had 3 points on the same line, then infinitely many planes are possible. Imagine the plane spins around the line as a sort of fan blade.
Choice A can be ruled out because points R, T, and S are all on the same line. They are collinear points. Using these three points is not enough to properly identity/label this plane, since infinitely many other planes could result.
Choices B and C can also be ruled out for similar reasons.
Choice D is correct because points P, Q, and Y are all in plane M, and also because they are not all on the same line.
Side note: another way to phrase "a plane is formed by 3 non-collinear points" is to say "a plane is formed by 3 points that form a triangle".