(a) (i) What is an acid?
(ii) Give two differences between an acid and a base, in terms
of taste and feel.

(b) (i) Define pressure.
(ii) A force of 200 N is exerted on an area of 50 m2.
Calculate the pressure exerted by the force.

(c) Explain the following terms as associated with living organisms:
(i) unicellular;
(ii) multicellular.

(d) Give two reasons why soil air is important.