A. A robot may not injure a human being or, through inaction, allow a human being to come to harm.
B. A robot must obey any orders given to it by human beings, except where such orders would conflict with the First Law.
C. A robot may not harm a human, or, by inaction, allow a human to come to harm, except when doing so would prevent greater harm to humanity.
D. A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.