What is the most suitable word that describes the work of a policeman according to the passage

A．he must be able to tell when and where a crime is committed
B．he must justify the arrests he makes of criminals
C．he must behave as professional lawyers do
D．he must work hard to help reform criminals

A．He has to justify his arrests while unable to provide sufficient evidence in most cases.
B．He has to provide the best possible public service at the least possible expense.
C．He has to get the most desirable results without breaking the law in any way.
D．He can hardly find enough time to learn criminal law while burdened with numerous criminal cases.