Заполните пропуски, выбрав правильную грамматическую форму.

1.The simplest digital device is any device which [a) can; b)could; c)must] count.

2.In ancient days man [a) learns; b) learned; c) has learned] to substitute beads for fingers to help him count.

3.The ancient Chinese simplified the [a) counted; b) to count; c) counting] board into abacus.

4.The Japanese improved the abacus making it [a)more efficient; b)much efficient; c)efficienter].

5.The tremendous speeds of computers and the flexibility [a) building; b) built; c) to build] into them [a) because of; b) according to; c) due to] the logical control make modern computers more powerful than mechanical calculators.

6.The big problem in understanding digital computers is the logic which relates the logical elements into a unit [a)performed; b) performing; c) having performed] arithmetic and logical operations.

7.Arithmetic operations [a) converted; b) are converted; c) was converted] into a sequence of simple logical operations.

8.Any digital calculation is usually [a) breaking; b) broken; c) being broken] down into a sequence of elementary operations.

9.A computer is a device [a) to accept; b) has accepted; c) accepts] a set of instructions and [a) executes; b) executed; c) to execute] them in the appropriate sequence.
lO.The flip-flop [a) is; b) was; c) has been] a storage cell with two inputs and two outputs.