The first two stages in the development of civilized man were probably the invention of weapons and the discovery of fire, although nobody knows exactly when he acquired the use of the _____.
句意： 人类文明发展的最初两个阶段很可能是武器的发明和用火，尽管没人知道人类是什么时候学会后者的。 指代两者中的后者用latter。 因此， 本题的正确答案为D。