Answer:
(a) Gas pressure ---------------------> (iii) force per unit area
(b) One mole of substance -------------------> (i) 6.02 x 10²³
(c) One mole of any gas ----------------------> (ii) 22.4 dm³ at STP
(d) Avogadro's number -----------------> (iv) 6.02 x 10²³ particles