The correct answer is C. MACSYMA.
MACSYMA is an expert system developed at MIT to solve mathematical problems. It was one of the first computer algebra systems, and it is still used today by mathematicians, engineers, and scientists.
RAND is a research organization that was founded in 1946. It is not an expert system.
ISIS is a computer program that was developed at the University of Maryland. It is not an expert system.
MOLGEN is a computer program that was developed at Stanford University. It is not an expert system.
CMU is a university in Pittsburgh, Pennsylvania. It is not an expert system.