What is the most important factor in the decision to arrest someone?

their attitude

the nature of the crime

the time of day

the evidence against the person

The most important factor in the decision to arrest someone is D.  The evidence against the person.

Explanation:

Knowleadge of evidence against the person is the most important factor in the decision to arrest someone. More specifically, the existance of facts and circumstances that would lead to believe that the suspect has committed or is committing a crime is called probable cause, and is the key element to decide whether to arrest someone or not. This reasoning must come from specific facts, circumstances and evidence, and not just from the officer's suspicion.

the use of email to replace slower surface mail.

to act quickly in times of danger to the united states

because you have to act quickly if you want to live/survive.