A. Abacus - अबेकस
B. Clock - घड़ी
C. calculator - कैलकुलेटर
D. None of these. - इनमे से कोई भी नहीं
Abacus, plural abaci or abacuses, calculating device, probably of Babylonian origin, that was long important in commerce. It is the ancestor of the modern calculating machine and computer.