Which of the following is still useful for adding numbers?

ANS:C - Abacus

EDSAC : Electronic Delay Storage Automatic Calculator (EDSAC) was an early British computer.

ENIAC : Electronic Numerical Integrator And calculator which was the first large-scale computer. which is 300 times faster than human speed.

Abacus : The abacus, also called a counting frame, is a calculating tool.

UNIVAC : ('UNIVersal Automatic Computer I) was the first commercial computer made in the United States.