题目

如图是兔和狼的牙齿结构示意图，请回答下列问题：（1）___________图是狼的牙齿．（2）与狼的牙齿相比，兔的牙齿没有_______的分化，这是与其吃植物性食物相适应的．（3）狼和兔均属于哺乳动物，它们的生殖特征是______________________．（4）与哺乳动物不同的是，鸟用坚硬的_____________啄取食物．（5）动物在生物圈中的作用是：（a）维持生态平衡，（b）帮助植物传份和传播种子，（c）____________．根据短文内容，从短文后的七个选项中选出能填人空白处的最佳选项。选项中有两项为 多余选项。Does a Dog Help a Teen with Low Self-esteem?A dog is known as man’s best friend for good reason. Loyal and affectionate ,a dog companion can enrich its owner’s life in many ways, 1_____ Many teenagers suffer from periods of low self-esteem (自尊）as they try to navigate the wavy waters of adolescence and deal with all of its associated highs and lows.A teenager who lacks self-esteem may feel isolated from his peers and unable to tell his parents about personal issues. The company of a dog can be a huge comfort and ease feelings of loneliness and awkwardness. A dog offers genuine unconditional love. 2_____All dogs need exercise，so taking his clog for a walk is the perfect opportunity for a teenager to get outdoors and benefit from fresh air and physical activity. Exercise allows people to take control of their bodies，which is often the first step toward regaining control of other aspects of their life，says mental health specialist Dr. Alan Cohen. 3    Exercise releases chemicals called endorphins (内排肽）into the brain? which create positive responses in the body ，including improved self­esteem.Dogs can help teenagers be more sociable and make new friends, suggests HELPGUIDE. 4_____ A dog is a great ice-breaker ，avoiding awkward social situations and putting the teenager at ease with people he meets. The more confident the teen becomes when out and about with his clog ，the more his self-esteem will improve.5_____ If a teenager is suffering from depression or developing dangerous habits such as alcohol and drug abuse ，more extreme action may be required. In these cases ，professional help should be sought and all treatment plans considered. Parents who suspect that their teen’s low self­esteem is a sign of a far more serious problem should ask a suitably qualified health professional for advice.A．In some cases, having a dog will not help with a teenager’s low self-esteem.B．It simply accepts its owner for who he is and doesn’t judge, question or criticize.C．Pets offer an unconditional love that can be very helpful to people with depression.D．You don’t have to worry about hurting your pet’s feelings or getting advice you don’t want.E. In particular, someone with low self-esteem may find a pet dog to be extremely beneficial.F. A teen may meet his peers while walking his dog in the park or taking part in a dog training class.G. Many forms of exercise besides walking can be enjoyed with a dog, such as cycling, jogging and throwing a ball.