What Is the Presumption Going into a Criminal Case in Reference

What is the presumption going into a criminal case in reference to the sanity of the defendant?

A) The defendant is insane and the prosecution must prove otherwise
B) The defendant is sane and the burden is on the defense to prove insanity
C) The requirement for proving sanity or insanity lies neither with the defense or prosecution but it is the judges responsibility to initiate the defense
D) Proof of insanity is not offered but inferred by observation by the jury