Which of the following time measuring

Option (d) is correct because a clock can measure time correctly up to one second. A stop watch can measure time correctly up to a fraction of a

second. A digital watch can measure time up to a fraction of second whereas an atomic clock is the most accurate timekeeper and is based on

characteristic frequencies of radiation emitted by certain atoms having precision of about 1 second in 300,000 years. So an atomic clock can

measure time most precisely as precision of this clock is about 1 s in 1013 s.