What Is the Main Difference Between a Systematic and a Random

What is the main difference between a systematic and a random measurement error in research?

A) A systematic error shows a difference between the true and observed measurement.
B) A random error occurs in the same way each time with each measurement taken.
C) A systematic error shows there was one or more transient factors in the measurement.
D) A random error occurs with unpredictably or by chance during the measurement.