The answer is D. The words and ideas are short-lived and disappear quickly.
Jacques Derrida, in some famous passages, particularly in Of Grammatology, makes a compelling argument about the fact that thought, therefore philosophy, was only able to be born once writing came to be. Writing can assure the permanence of what is no longer present, a thought, an idea, an impression, even after the author has long disappeared. Speaking, on the other hand, has a vivid though short lived influence on the mind, and since speaking is ephemeral, so are the ideas and the words that are spoken.