Dogs have been man's good friends for t______ of years.Many stories told how brave dogs helped

Dogs have been man's good friends for t______ of years.Many stories told how brave dogs helped
people in t______.With the help of dogs,many people l______ in snow found their way home.
Dogs have also helped in many scientific researches(科学研究).The first spacetraveller was a dog n______ Laika.It was sent up in a manmade satellite(人造卫星)in 1957 by R______ scientists.
Dogs have become film stars,too.A dog called Lassie was the star in quite a few American f______.
Dogs can h______ and s______ better than man,but they can not see so well.A dog may l______ for about 12 or 13 years.A thirteen-year-old child is not grown up yet,b______ a thirteen-year-old dog is a very old dog indeed.
people in t______.With the help of dogs,many people l______ in snow found their way home.
Dogs have also helped in many scientific researches(科学研究).The first spacetraveller was a dog n______ Laika.It was sent up in a manmade satellite(人造卫星)in 1957 by R______ scientists.
Dogs have become film stars,too.A dog called Lassie was the star in quite a few American f______.
Dogs can h______ and s______ better than man,but they can not see so well.A dog may l______ for about 12 or 13 years.A thirteen-year-old child is not grown up yet,b______ a thirteen-year-old dog is a very old dog indeed.