Adam Smith and David Ricardo, is the right answer.
Alfred Marshall is regarded as one of the best economists of his age. He is one who was involved in the founding of one of the most influential School of Economics known as the Neoclassical School. Although his economics was promoted as additions and distillations of the practice of Adam Smith, David Ricardo and some others, he prolonged economics away from its classical locus on the market economy and rather generalized it as a study of human behavior.
