GO Classes DPP | Propositional logic | Implication | Kenneth H.Rosen

Answer 1

Answer: A,B,D
While checking tautology for implications, check whether we can make $\mathrm{T} \rightarrow \mathrm{F}$, because that is the only combination that can make a implication false.

Try to make RHS as false by keeping LHS as True.
Let's check every option in the question
Option A: LHS is true only when both P and Q are T, RHS can't be false here. Hence tautology

Option B: Here if P is T, then it makes P V Q to True, Hence tautology
Option C: Here counter example is $\mathrm{P}=\mathrm{T}$ and $\mathrm{Q}=\mathrm{F}$, makes the expresssion false, hence not tautology

Option D: LHS is true when both P and Q are T, if both are T then P $\rightarrow$ Q is Also true, so we can't have something like $\mathrm{T} \rightarrow \mathrm{F}$. Hence tautology.

Answer 2

A, b, d

Answer 3

A,B,D is correct

Answer 4

C cant be since taking P as true and Q as false make it false hence there exists a condition where we can make it false hence implies it is not tautology and it is contingency
rest are tautology

Answer 5

Option A, B ,D 

Answer 6

correct options : A , B , D