Which of the following is true about the verdict of "guilty but mentally ill"?

A) It has been adopted by some states as an alternative to the verdict of "not guilty by reason of insanity."
B) Defendants convicted under this standard serve their entire sentence in mental institutions.
C) Defendants convicted under this standard serve their sentence in a mental institution until it is determined that they are no longer mentally ill; then they finish their sentence in prison.
D) Defendants convicted under this standard are given the option of either going to jail, or receiving treatment for their mental illness.