Câu hỏi:

Read the following passage and mark the letter A, B, C or B on your answer sheet to indicate the correct answer to each of the questions from 30 to 34.

  If parents bring up a child with the sole aim of turning the child into a genius, they will cause a disaster. According to several leading educational psychologists, this is one of the biggest mistakes which ambitious parents make. Generally, the child will be only too aware of what his parents expect, and will fail. Unrealistic parental expectations can cause great damage to children.

  However, if parents are not too unrealistic about what they expect their children to do, but are ambitious in a sensible way, the child may succeed in doing very well — especially if the parents are very supportive of their child. Michael Collins is very lucky. He is crazy about music, and his parents help him a lot by taking him to concerts and arranging private piano and violin lessons for him. They even drive him 50 kilometers twice a week for violin lessons. Michael's mother knows very little about music, but his father plays the trumpet in a large orchestra. However, he never makes Michael enter music competitions if he is unwilling.

  Winston Smith, Michael's friend, however, is not so lucky. Both his parents are successful musicians, and they set too high a standard for Winston. They want their son to be as successful as they are and so they enter him for every piano competition held. They are very unhappy when he does not win. Winston is always afraid that he will disappoint his parents and now he always seems quiet and unhappy.

The two examples given in the passage illustrate the principle that _________.