题目内容：

People think the dog is the most useful animal in the w(). Some people keep a dog to h() them
in the fight against other animals.Some people keep a dog t() frighten thieves.Others use a dog to drive sleep and protect chickens.
But m() people look upon a dog as their friend,just like a member of the f() .
the
m
是them

优质解答

People think the dog is the most useful animal in the world.Some people keep a dog to help them in the fight against other animals.Some people keep a dog to frighten thieves.Others use a dog to drive ...