Is triangle MNP isosceles?

[BTGModeratorVI]

Is triangle MNP isosceles?

(1) Exactly two of the angles, M and N, have the same measure.
(2) Angles N and P do not have the same measure.

Source: Official Guide
Answer: A

[Brent@GMATPrepNow]

Is triangle MNP isosceles?

(1) Exactly two of the angles, M and N, have the same measure.
(2) Angles N and P do not have the same measure.

Source: Official Guide
Answer: A

Target question: Is triangle MNP isosceles?

Statement 1: Exactly two of the angles, M and N, have the same measure.
Perfect. This is the precise definition of an isosceles triangle
The answer to the target question is YES, triangle MNP is isosceles
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: Angles N and P do not have the same measure
Here are two conflicting scenarios that satisfied statement 2
Case a: ∠N = 50°, ∠P = 80°, and ∠M = 50°. In this case, the answer to the target question is YES, triangle MNP is isosceles
Case b: ∠N = 50°, ∠P = 70°, and ∠M = 60°. In this case, the answer to the target question is NO, triangle MNP is not isosceles
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer: A

Cheers,
Brent