骨龄什么时候闭合

Trainer Fu Mingyan trains a guide dog in Dalian, northeast China's Liaoning Province, April 22, 2021. The Dalian branch of the China Guide Dog Training Center, which was founded in May 2006, is a non-profit training institution of guide dogs in China. It has provided 239 free guide dogs to visually impaired people around the country. Guide dogs in the center are strictly selected from Labrador and Golden retrievers. Usually 45 days after birth, those puppies are sent to live with volunteer families, getting familiar with human life and learning simple orders. When the puppies grow up to about one year old, they are sent back to the center for professional training for one to one and a half year. Customized courses which are specially set according to the life scenes of visually impaired people, include going up and down stairs, avoiding obstacles and crossing streets. They also take a series of "exams", and the assessment of their characters is an important item. Those dogs that have a tendency to attack people will be dismissed. After completing all trainings, guide dogs will attend a 40-day joint training with visually impaired users. Every day, the users go out with guide dogs under the guidance of staff. Only when the two sides cooperate well and successfully pass the joint training period can the guide dog obtain a "graduation certificate" and be delivered to users. (Xinhua/Pan Yulong)