单项选择题

Directions: This part is to test your reading ability. There are 5 tasks for you to fulfil. You should read the reading materials carefully and do the tasks as you are instructed.
Task 1
Directions: After reading the following passage, you will find 5 questions or unfinished statements, numbered 36 through 40. For each question or statement there are 4 choices marked A), B), C) and D ). You should make the correct choice and mark the corresponding letter on the Answer Sheet with a single line through the centre.

Methods of training animals have changed greatly in recent years. Zoo keepers have always had problems getting the animals to leave their cages in order for the cages to be cleaned, and also training them to move indoors when appropriate. Another problem was that many of the large animals became listless and bored. In the last twenty years, scientists have done research on dolphins and whales, training them to obey commands. The scientists found they could get animals to obey by rewarding them with food and affection when they responded correctly. Proper training allows the animals to receive the care they need. It was very difficult to get untrained animals, especially the larger ones, to stay still when they needed medical attention. Now they can be trained, on command, to remain still and even to allow blood samples to be taken and shots administered. All this is accomplished through positive reinforcement, without the use of any force. Affection training, as this process is called, has been used with great success on a wide variety of zoo animals. Animal behavior experts have taught zoo keepers to train bears, tigers, monkeys, and many other species to behave in a way that provides for better animal-keeper interaction. This training also keeps the animals from becoming bored and inactive.

Affection training has been used successfully on ______.