Match List-I with List-II:
List-I                                                              List-II
(a) Ca(OCl)$$_2$$                                         (i) Antacid
(b) CaSO$$_4$$ . $$\frac{1}{2}$$H$$_2$$O                               (ii) Cement
(c) CaO                                                    (iii) Bleach
(d) CaCO$$_3$$                                             (iv) Plaster of paris
Choose the most appropriate answer from the options:

Let us match each calcium compound with its correct use:

(a) Ca(OCl)$$_2$$ is calcium hypochlorite, commonly known as bleaching powder. It is used as a bleach. So (a) matches with (iii).

(b) CaSO$$_4$$ · $$\frac{1}{2}$$H$$_2$$O is calcium sulphate hemihydrate, known as Plaster of Paris. So (b) matches with (iv).

(c) CaO is calcium oxide, also called quicklime. It is a key ingredient in the manufacture of cement. So (c) matches with (ii).

(d) CaCO$$_3$$ is calcium carbonate, which is used as an antacid to neutralize stomach acid. So (d) matches with (i).

The correct matching is: a-iii, b-iv, c-ii, d-i.

The answer is $$\boxed{\text{a-iii, b-iv, c-ii, d-i}}$$.