GATE | CS | 2003 | Discrete Mathematics | Set Theory | Question 31

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Let (5, ≤) be a partial order with two minimal elements a and b, and a maximum element c.

Let P : S → {True, False} be a predicate defined on S.
Suppose that P(a) = True, P(b) = False and
P(x) ⇒ P(y) for all x, y ∈ S satisfying x ≤ y,
where ⇒ stands for logical implication.

Which of the following statements CANNOT be true ?

P(x) = True for all x ∈ S such that x ≠ b

P(x) = False for all x ∈ S such that x ≠ a and x ≠ c

P(x) = False for all x ∈ S such that b ≤ x and x ≠ c

P(x) = False for all x ∈ S such that a ≤ x and b ≤ x

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