2.a system error B accidental error C system error D system error E accidental error F accidental error H accidental error

Systematic error: also known as regular error, refers to the measurement error that the values and symbols in the measured value sequence remain unchanged or change according to a certain law under the same measurement conditions.

Accidental error: also known as random error, refers to the measurement error that the number and symbol of the measured value sequence are uncertain under the same measurement conditions, but obey certain statistical laws.

3. Revision: Q =1.61*10e-19+-0.29 *10e-19.