"Physicalists" expect that ultimately all mental functions will be explainable in neurobiological terms. Achieving this goal requires knowledge of neurons and their basic functions, a knowledge of how neurons interact, and a delineation of the psychological faculties to be explained. At present, there is a substantial amount of fundamental knowledge about the basic functions of neurons, and the scope and character of such psychological capacities as visual perception and memory are well understood. Thus, as the physicalists claim, mental functions are bound to receive explanations in neurobiological terms in the near future. Which one of the following indicates an error in the reasoning in the passage? ['The passage does not indicate that any knowledge has been achieved about how neurons interact.', 'The passage fails to describe exactly what is currently known about the basic functions of neurons.', 'The word "neurobiological" is used as though it had the same meaning as the word "mental. "', 'The conclusion contradicts the claim of the physicalists.']