The correct answer is C, Hamlet does not want to murder Claudius while he is praying because he does not want him to die while he is confessing his sins, which may result in him going to Heaven.
A very important part of this play is revenge and punishment, so Hamlet doesn0t want to be the person that sends his father's murderer to heaven it is not only the fact that he is praying and in case he dies while he talks to god he might go to heave it is about being him the one who is supposed to make him pay for his sins, free him from the same.
Options A, B, and D are not possible answers because A) Hamlet has been in many battles blood is for sure something he's not afraid of, B) By this time of the play he is fully sure who the killer of his father is and D) He's is always armed and ready to either protect himself o punish his father's murderer.