Final answer:
The slang term that can mean 'diamonds' or 'to kill' to a criminal is 'Hit'. It is used to obscure the true intent of criminal conversations.
Step-by-step explanation:
To a criminal, the slang term that can mean both diamonds and to kill is A) Hit. This term is dual-purpose in the underworld vernacular, whereby taking out a hit may refer to contracting a murder or could be used in a less violent context to refer to acquiring some diamonds, potentially through theft. In the world of crime, these terms are often embedded in covert language to disguise the true intent of a conversation from law enforcement and the uninitiated.