Quinn or Raina will be valedictorian. Quinn's being valedictorian entails that she receives an A+ in Spanish. She doesn't receive an A+ in Spanish. So, Raina is valedictorian.
-Working backward from the conclusion of this argument, which of the following is the most likely justification of the last step of the derivation?
A) MP
B) MT
C) HS
D) DS

Question

Quizplus · Accepted Answer

The argument uses Disjunctive Syllogism (DS), which states that if one of the disjuncts is false, the other must be true. Since Quinn is not valedictorian, Raina must be.

Quinn or Raina Will Be Valedictorian