单项选择题

TEXT B
That man is an aggressive creature will hardly be disputed. With the exception of certain rodents, no other vertebrate habitually destroys members of his own species. No other animal takes positive pleasure in the exercise of cruelty upon another of his own kind. We generally describe the most disgusting examples of man’s cruelty as brutal, implying by these adjectives that such behavior is characteristic of less highly developed animals than ourselves. In truth, however, the extremes of "brutal" behavior are confined to man; and there is no parallel in nature to our savage treatment of each other. The depressing fact is that we are the cruelest and most ruthless species that has ever walked the earth; and that, although we may shrink back in horror when we read in newspaper or history book of the brutalities committed by man upon man, we know in our hearts that each one of us harbors within ourselves those same savage impulses which lead to murder, to torture and to war.
To write about human aggression is a difficult task because the term is used in so many different senses. Aggression is one of those words which every one knows, but which is nevertheless hard to define. As psychologists use it, it covers a very wide range of human behavior. The red-faced infant squalling for the bottle is being aggressive; and so is the judge who awards a thirty-year sentence for robbery. The guard in a concentration camp who tortures his helpless victim is obviously acting aggressively. Less manifestly, but no less certainly, so is the neglected wife who threatens or attempts suicide in order to regain her husband’s affection. When a word becomes so diffusely applied that it is used both of the competitive striving of a footballer and also of the bloody violence of a murderer, it ought either to be dropped or else more closely defined. Aggression is a combined term which is fairly bursting at its junctions. Yet until we can more clearly designate and comprehend the various aspects of human behavior which are subsumed under this head, we cannot discard the concept.
One difficulty is that there is no clear dividing line between those forms of aggression which we all deplore and those which we must not disown if we are to survive. When a child rebels against authority it is being aggressive; but it is also manifesting a drive towards independence which is a necessary and valuable part of growing up. The desire for power has, in extreme form, disastrous aspects which we all acknowledge; but the drive to conquer difficulties, or to gain mastery over the external world underlies the greatest of human achievements. Some writers define aggression as "that response which follows frustration", or as "an act whose goal-response is injury to an organism (or organism surrogate)". In the author’s view these definitions impose limits upon the concept of aggression which are not in accord with the underlying facts of human nature which the word is attempting to express. It is worth noticing, for instance, that the words we use to describe intellectual effort are aggressive words. We attack problems, or get our teeth into them. We master a subject when we have struggled with and overcome its difficulties. We sharpen our wits, hoping that our mind will develop a keen edge in order that we may better divide a problem into its component parts. Although intellectual tasks are often frustrating, to argue that all intellectual effort is the result of frustration is to impose too negative a coloring upon the positive impulse to comprehend and master the external world.
According to the author, the concept of "aggression" ______.