Which of these is the 'Identity Law' for conjunction?
P∧P≡PP \land P \equiv PP∧P≡P
P∧1≡PP \land 1 \equiv PP∧1≡P
P∧0≡0P \land 0 \equiv 0P∧0≡0
P∧1≡1P \land 1 \equiv 1P∧1≡1