After a crime has been reported, what is one of the first decisions that the police have to make?

who is guilty

whether to arrest the suspect

whether to investigate the crime

whether to recommend the death penalty

C.Whether to investigate the crime.

You have no suspect unless you have the witness with you to find the suspect so you can not arrest or announce someone guilty.
 If there was a witness, or the witness saw the crime you could not arrest the suspect(s) but bring them in for questioning because of the lack of evidence from not investigating

 The crime needs to be investigated, depending on what crime it is, the death penalty is not suitable for a robbery