What is the si unit of time? name four multiples-

Answer(b) 60 miles per hour;

If its history of, then b) because a) implies only present day (now)

Answer175 to 225 degreeswhite

Repeated trials allow you to calculate a mean which can reduce the effect of random errors to make your results more precise.your results will also be reproducible therefore if someone else did the same experiment they'd get the same results which would make your results more reliable.