A、From three to five months. B、Three months. C、Five months. D、Four months. AHow long does the intensive course last?

A guide dog is a dog especially trained to guide a blind person. Dogs chosen for such training must show good intelligence, physical fitness, and responsibility.
    At the age of about fourteen months, a guide dog begins an intensive course that lasts from three to five months. It becomes accustomed to the leather harness and stiff leather handle it will wear when guiding its blind owner. The dog learns to watch traffic and to cross streets safely. It also learns to obey its owner’s commands.
    The most important part of the training course is a four-week program in which the guide dog and its future owner learn to work together. However, many blind people are unsuited by personality to work dogs. Only about a tenth of the blind find a guide dog useful.