Research is an important part of understanding how eyewitness accounts are derived. As such, a range of factors are often considered. Those factors that are within the control of the justice system are:
system variables

Research is an important part of understanding how eyewitness accounts are derived. As such, a range of factors are often considered. Those factors that are within the control of the justice system are system variables

Explanation:

System variables consists of instructions given to eyewitness.The System variable is predefined and they cannot be changed. These variables are under the control of the justice system. These variables influence the accuracy of eyewitness in identification.

The System variable consists of all those ways which are used by the police to ask a question to a witness and procedure used to help the witness in identifying the person who has committed the crime.

it should be d or b but i'm sure it's d