To prove any wff valid or tautology try to use this analogy.
Since implication A->B is FALSE only when A=T and B=F.So to prove any implication is valid or not try to get TRUE->FALSE if we succeed then it is not valid,if we not then wff is valid.
So for option A
substitute P=T and R=F
RHS P->R become FALSE
LHS (P->Q)^(P->R)
To get true here we need T^T so substitute Q=T which makes P->Q TRUE and P->R FALSE so T^F=F which makes LHS=FALSE.
Hence we are unable to get T->F which proves wff given in OPTION A is valid.
NOTE: we can use similar kind of logic to prove contradiction.