Answer:
Option B
Explanation:
Suppose, P1 is a truth-teller.As exactly one of them is a liar, second statement of P2 or P3 must be false. But if the second statement of P2 is false, then P3's second statement must be false.
Therefore, P2's first statement is true.
Therefore, P3's first statement must be false .
Suppose P2 is a truthteller, then P3 is P.
Therefore, P3's second statement is true.
$\Rightarrow$ P3's first statement must be false
Therefore, P1 must be an alternator.
P1's second statement must be false
Therefore P1 is Q.
$\Rightarrow$P2 is R.
If P3's both the statements are true,which is not possible as it violates the conditions given by P2 and P1.