A．Because they were afraid of being assigned dangerous ……

TEXT A
A common result of being frustrated is an act of aggression, sometimes violent. To be alive is to have a goal and pursue it — anything from cleaning the house, or planning a vacation, to saving money for retirement. If somebody or something blocks the goal, we begin to feel pent up and thwarted. Then we get mad. The blocked goal, the sense of frustration, aggressive action —this is the normal human sequence. If we are aware of what is going on inside us, however, we can save ourselves a good deal of needless pain and trouble.
Everyone has encountered frustration on the highways. You are driving along a two-lane road behind a big trailer-truck. You’re in a hurry, while the truck driver seems to be enjoying the scenery. After miles of increasing frustration you grow to hate him. Finally you step on the gas and pass him defiantly, regardless of the chance you may be taking. This kind of frustration must cause thousands of accidents a year. Yet, if you realized what was going on in your nervous system, you could curb such dangerous impulses.
The aggressive act that frustration produces may take a number of forms. It may be turned inward against oneself, with suicide as the extreme example. It may hit back directly at the person or thing causing the frustration. Or it may be transferred to another object — what psychologists call displacement. Displacement can be directed against the dog, the parlor furniture, the family or even total strangers.
A man rushed out of his front door in Brooklyn one fine spring morning and punched a passerby on the nose. In court he testified that he had had a quarrel with his wife. Instead of punching her he had the bad luck to punch a police detective.
Aggression is not always sudden and violent; it may be devious and calculated. The spreading of rumors, malicious gossip, a deliberate plot to discredit, are some of the roundabout forms. In some cases, frustration leads to the opposite of aggression, a complete retreat from life.
The classic pattern of frustration and aggression is nowhere better demonstrated than in military life. GIs studied by the noted American sociologist Samuel A. Stouffer in the last war were found to be full of frustrations due to their sudden loss of civilian liberty. They took it out verbally on the brass, often most unjustly. But in combat, soldiers felt far more friendly toward their officers. Why Because they could discharge their aggression directly against the enemy.
Dr. Karl Menninger, of the famous Menninger Foundation at Topeka, pointed out that children in all societies are necessarily frustrated, practically from birth, as they are broken into the customs of the tribe. A baby’s first major decision is "whether to holler or swaler" —when it discovers that the two acts cannot be done simultaneously. Children have to be taught habits of cleanliness, toilet behavior, regular feeding, punctuality; habits that too often are hammered in.
Grownups with low boiling points, said Dr. Menninger, probably got that way because of excessive frustrations in childhood. We can make growing up a less difficult period by giving children more love and understanding. Parents in less civilized societies, Menninger observes, often do this. He quotes a Mohave Indian, discussing his small son: "Why should I strike him He is small, I am big. He cannot hurt me."
When we do experience frustration, there are several things We can do to channel off aggression. First, we can try to remove the cause which is blocking our goal. An individual may be able to change his foreman, even his job or his residence, if the frustration is a continuing one.
If this cannot be done, then we can seek harmless displacements. Physical outlets are the most immediately helpful. Go out in the garden and dig like fury. Or take a long Walk, punch a bag in the gym, make the pins fly in a bowling alley, cut down a tree. The late Richard C. Tolman, a great physicist, once told me that he continued tennis into his 60s because he found it so helpful in working off aggressions.
As a writer I receive pan letters as well as fan letters, and some of them leave me baffled and furious. (Some, I must admit, are justified. ) Instead of taking it out on the family, I write the critic the nastiest reply I can contrive. That makes me feel a lot better. Next morning I read it over with renewed satisfaction. Then I tear it up and throw it in the wastebasket. Aggression gone, nobody hurt.
But perhaps the best way of all to displace aggressive feelings is by hard, useful work. If both body and mind can be engaged, so much the better.
The world is filled today with a great surplus of anger and conflict. We are far from knowing all about the sources of these destructive feelings, but scientists have learned enough to clear up quite a load of misery. Their findings can help us reduce that load and even utilize its energy, through a better understanding of ourselves and our neighbors.
According to Stouffer, why were GIs much more friendly towards their officers in combat

A．Because they were afraid of being assigned dangerous tasks.
B．Because they could release their pent-up frustration against the enemy.
C．Because they were more like equals and friends in face of enemy.
D．All of the above.