Final answer:
The correct option for the LISP function named AREATRIANGLE is A. (defun AREATRIANGLE (base height) (* 0.5 base height)).
Step-by-step explanation:
The correct option for the LISP function named AREATRIANGLE is A. (defun AREATRIANGLE (base height) (* 0.5 base height)). This function takes the base and height as parameters and returns the area of the triangle. The formula for calculating the area of a triangle is 1/2 times the base times the height.