Animals perform. many useful entertaining jobs. Dogs are particularly valuable in guiding the blind, protecting property, finding losing 【M1】 ______ people, and hunting criminals. Horses are used in guarding herds, carrying men in lands that there are no roads, and helping farmers work their 【M2】 ______ land. Pigeons have long used to carry messages. Wild animals from the 【M3】 ______ jungles, forests and seas are very popular performers in circuses and moving pictures. People realized that, although animals may not have same 【M4】 ______ intelligence as human beings, they are enough smart to learn certain things. 【M5】 ______ The first thing a dog taught is to obey. It should not take too long for 【M6】 ______ him to learn commands. Simple orders, such as 'sit, lie down, stay there, come here,' can even be taught by a child. Training a dog to be a watchdog often produces unexpected results. Soma dogs quickly learn the differences between unwanted people from 【M7】 ______ friends. This is because their masters welcome friends and invites them into their house. However, some dogs will always attack the postman who goes to deliver letters. One explanation for this behaviour is that, 【M8】 ______ the postman comes to the house often, he never enters the house. Therefore, 【M9】 ______ the dog thinks the postman is someone who is not wanted, but keeps to come back anyway. 【M10】 ______ 【M1】