The invention of both labor-saving tools and tools of intelligence is rarely accidental. I
(30) civilizations developed, greater work efficiency came to be demanded, and (31) tools became more (32) . A tool would (33) a function until it proved (34) in meeting human needs, at which point an improvement would be made. One impetus for invention has always been the (35) for speed and high-quality results--provided they are achieved (36) reasonable costs. Stone pebbles were sufficient to account for small quantities of possessions, (37) they were not efficient enough for performing sophisticated mathematics. However, beads arranged systematically evolved into the abacus. The (38) of this tool can be (39) to the development of commerce in the East around 3000 B.C., and the abacus is known (40) by the ancient Babylonians, Egyptians, Chinese, etc.
A.imagination
B.creativity
C.necessity
D.illusion