Why are many trials taken and averaged in an experiment?

Many trials are taken and averaged in an experiment to reduce the measurement error.  

A great manner by which error is reduced or to enhance the accuracy of measurement is to take many measurements and compute their average. In other terms, one attain accuracy via averaging.  

This also validates the repeatability of the measurement. The kinds of experimental error include mistakes in data entry, human error, mistakes in the design of the experiment, or systematic error, or random error due to environmental circumstances.  

answer; i believe the correct answer to the above question is ( friction)

sulfur dioxide

explanation: acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. these substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.