This article is mainly about ______.

We know that, for the most part, the bigger a man’s muscles are, the stronger he is. (18[C])Can it be claimed, then, that the larger the brain a man possesses, the smarter he is? The answer is no.
     There are only two animals that have larger brains than man, the whale and the elephant. Yet, in proportion to his size, man’s brain is larger. (19[C])Man’s usually weighs about three pounds or a little more, and this is about one-fortieth of the weight of his whole body. The whale’s body, on the other hand, is a thousand times heavier than its brain, while the elephant’s body is about five hundred times as heavy.
     But a man who has a large brain is not necessarily more intelligent than one whose brain is smaller. We know that geniuses have existed who have had very large brains, but there have been others whose brains were rather small. Idiots have been known to have very large brains.
    (20[D])We do not understand precisely why some people are more intelligent than others. Whether our brains are relatively large or small is less important than that we try to do our very best.