A．animals depend on each other

　　B．birds depend on animals for food

　　C．both sides can get help

　　D．not all animals treat their partners well

　　解析：选D　推理判断题。由文章第二、三、四段可知，有共生现象的动物中，有的是相互得到帮助，而有的是单方面的。故答案为D项。

　　3．When plovers hop into crocodiles' mouths, they ________.

　　A．are really to clean crocodiles' teeth

　　B．are to make crocodiles happy

　　C．aren't afraid of being eaten

　　D．aren't happy to clean the crocodiles' teeth

　　解析：选C　细节理解题。由文章最后一段可知，plovers 是不担心被鳄鱼咬伤的，因为鳄鱼是希望 plovers 这样做的，而对于 plovers 而言，其真正的目的是为了得到自己的食物。故答案为C项。

　　4．According to the text, it can be inferred that ________.

　　A．living in the wild can be hard

　　B．different animals have different living ways

　　C．crocodiles mainly live on plovers

　　D．ticks are useful to some animals

　　解析：选B　推理判断题。文章第一段就提到有些动物是靠自己去捕捉食物，而文章又举例讲了一些动物是靠共生来获取食物的，也就是说不同的动物有不同的方式来生存，所以答案为B项。选项A是文章直接叙述的；选项C表达与原文不一致；选项D是无法推断出的。

　　Ⅱ.阅读七选五

　　SOCIALIZING YOUR DOG

　　Keep it fun and enjoyable

　　Socialization shouldn't feel like work because it's really just a natural process dogs must go through to enjoy their time with other dogs and humans.__1__. They'll help reduce any anxiety produced by an unfamiliar experience. Bringing a few of your dog's favorite toys along can also help keep your puppy entertained and relaxed while visiting a new place.

　　Your dog should lead the way, not you

__2__.When introducing them to another puppy, let both dogs smell each other (that's their way of saying hello) while holding onto their leash (狗链). If one becomes fearful or aggressive,