What Do Immediate Impact Studies Indicate About Capital Punishment's Deterrent

What do immediate impact studies indicate about capital punishment's deterrent effect on murder?

A) Impact studies indicate that the overall impact of executions might actually increase the incidence of homicide.
B) Impact studies indicate that a deterrent effect does not exist, even though the death penalty is being used more often over the past decade.
C) Impact studies are inconclusive regarding capital punishment's deterrent effect on murder.
D) Impact studies indicate a deterrent effect, but only for expressive forms of murder.