P and Q are two propositions. Which of the following logical expressions are equivalent?

(A) Only I and II
(B) Only I, II and III
(C) Only I, II and IV
(D) All of I, II, III and IV


Answer: (B)

Explanation: I and II are same by Demorgan’s law

The IIIrd can be simplified to I.

since is true always

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