Question

From the History of Clocks

Time 1) ... one of the most important measurements of modern life. It is
impossible to imagine our working day without a clock or a watch. The history of
clocks is very long and there 2) ... many different types of clocks over the centuries.
The word ‘clock’ 3) ... from the Latin «сіосса». People 4) ... to use this word in the
14th century. The first clocks in the history of mankind 5) ... sundials or sun clocks.
Sundials 6) ... about 5.500 years ago and about 3.400 years ago water clocks were
invented. Since somebody 7) ... dividing day and night into hours and minutes, the
inventors 8)... numerous types of clocks like pendulum clocks, cuckoo clocks,
mechanical clocks and watches and quartz crystal clocks and watches. Jost Burgi 9)...
the first clock with a minute hand in 1577. Perhaps the most significant step forward
in the history of time measurement 10) ... the introduction of the mechanical clock
with wheels. It 11) ... in the 12th century and people 12)... to set the clocks on the
towers of churches. Quartz crystal clocks 13)... in 1920.
1) a) became; b) has become.
2) a) were; b) have been.
3) a) came; b) has come.
4) a) started; b) have started.
5) a) were; b) have been.
6) a) appeared; b)have appeared.
7) a) suggested; b) has suggested.
8) a) created; b) have created.
9) a) invented; b) has invented.
10) a) was; b) has been.
11) a)happened; b) has happened.
12) a) began; b)have begun.
13) a) appeared; b)have appeared.