In the following passage there are blanks which are numbered. Below the passage against these words, a choice of four words, marked (A), (B), (C) and (D) is given, One of which fits the blank appropriately. Find the appropriate word.

Primitive man was perhaps more concerned (1) fire as a source of warmth and as a means of cooking food than as a source of light. (2) he discovered less laborious ways of making fire, he had to (3) it and (4) he went on journey he carried a firebrand with him. His discovery that the firebrand, from which the torch may well have developed, (5) used for illumination was probably (6) to the (7) purpose of preserving a flame. Lamps, too, were developed by accident. Early man (8) his first conception of lamp (9) watching a twig or fibre burning in the molten fat (10) from a roasting carcass. All he had (11) was to fashion a vessel to contain fat and float a lighted reed in it. Such lamps, which were made of stones or sea shells have persisted in identical form up to (12) recent times.