Some snakes eat other snakes, even poisonous ones. The poison does not do them any harm . Snakes can swallow  things that are bigger around than they themselves are. This is possible because the jawbones  are loosely joined, and the mouth can stretch to make room for a fat animal. The snake's slim body stretches to make space for the animal when it is inside. Many snakes eat birds' eggs or frogs . Others eat pests , mice and other animals that harm crops on farms. Because snakes do this valuable work, you should never kill one. It is too dangerous for you to kill a poisonous one. Leave that job to experts. In writing this passage the writer mainly wants us to  _
have a better impression  about snakes like snakes kill snakes with the help of experts regard snakes as one of man's best friends