Essayist: Common sense, which is always progressing, is nothing but a collection of theories that have been tested over time and found useful.When alternative theories that prove even more useful are developed, they gradually take the place of theories already embodied in common sense. This causes common sense to progress, but, because it absorbs new theories slowly, it always contains some obsolete theories.

If all of the essayist’s statements are true, then which one of the following must be true?

(A) At least some new theories that have not yet been found to be more useful than any theory currently part of common sense will never be absorbed into the body of common sense. We cannot say that some theories that have not found to be useful will never belong to common sense. They may prove to be useful later on and then absorbed into the common sense.

(B) Of the useful theories within the body of common sense, the older ones are generally less useful than the newer ones. The main thing to notice here is "Of the useful theories". We know that when new more useful theory, the existing theory becomes obsolete. So, this statement excludes such theories. Out of the remaining useful theories, we cannot say whether the old or new one is more useful.

(C) The frequency with which new theories are generated prevents their rapid absorption into the body of common sense. The essayist never discussed the frequency of new theories.

(D) Each theory within the body of common sense is eventually replaced with a new theory that is more useful. Not true. The existing theory can remain useful indefinitely since no more useful theory was developed.

(E) At least some theories that have been tested over time and found useful are less useful than some other theories that have not been fully absorbed into the body of common sense. Since essayist says that some obsolete (less useful) theory always exist, we can say some theories (obsolete) are less useful than some other theories (more useful) that have not been fully absorbed.