Why do scientists need a standard system of measurement?
a. to allow for consistency with measurement data
b. in order to use tools marked in customary units
c. so they can keep measurement data confidential
d. to record measurements with easier abbreviations

Scientists need a standard system of measurement to allow for consistency with measurement data (A). Scientists would not be able to understand what other scientists are saying if everyone uses their own system of measurement. Scientists need to take measurements, interpret them and communicate the results to other scientists. That is why a standardized system of taking measurements has been developed. The International System of Units or the Metric system is the measurement system of choice for scientists all over the world today. 

Abecause its more effective