将分式方程1－$\frac{5}{x\left(x+1\right)}$＝$\frac{x+2}{x+1}$去分母后得(　　)．

    The Marches were a happy family, Poverty, hard work, and even the fact that Father March was away with the Union armies could not down the spirits of Meg, Jo, Beth, Amy, and Marmee, as the March girls called their mother.

    The March sisters tried to be good but had their share of faults. Pretty Meg was often displeased with the schoolchildren she taught; boyish Jo was easy to become angry; golden-haired schoolgirl Amy liked to show up; but Beth, who kept the house, was loving and gentle always.

    The happy days passed and darkness came when a telegram arrived for Mrs. March. “Your husband is very ill,” it said, “come at once.” The girl tried to be brave when their mother left for the front. They waited and prayed. Little Beth got scarlet fever (猩红热) when she was taking care of the sick neighbor. She became very ill but began to recover by the time Marmee was back. When Father came home from the front and at that joyful Christmas dinner they were once more all together.

    Three years later the March girls had grown into young womanhood. Meg became Mrs. Brooke, and after a few family troubles got used to her new state happily. Jo had found pleasure in her literary efforts. Amy had grown into a young lady with a talent for design and an even greater one for society. But Beth had never fully regained her health, and her family watched her with love and anxiety.

    Amy was asked to go and stay in Europe with a relative of the Marches'. Jo went to New York and became successful in her writing and had the satisfaction of seeing her work published there. But at home the bitterest blow was yet to fall Beth had known for some time that she couldn't live much longer to be with the family and in the spring time she died.

    News came from Europe that Amy and Laurie, the grandson of a wealthy neighbor, had planned to be married soon. Now Jo became ever more successful in her writing and got married to Professor Bhaer and soon afterwards founded a school for boys.

    And so the little women had grown up and lived happily with their children, enjoying the harvest of love and goodness that they had devoted all their lives to.

据权威机构调查，在某省违法犯罪的未成年人当中，有近50%的未成年犯存在网络依赖，有60%的未成年犯受到过网络、手机等不良信息的影响。这给我们的启示是（    ）

①网络的应用是一把双刃剑，有利也有弊                        ②要提高自己的辨别、觉察能力，提高自己的抗诱惑能力

③网络给青少年带来了许多问题，我们要远离网络        ④我们上网要遵守到的，更要遵守法律

材料分析题：
材料一：《达尔文的悲剧》
达尔文是19世纪伟大的生物学家，也是进化论的奠基人。然而在他还没有掌握大自然中生物界的奥秘之前，自己先受到了自然规律的无情惩罚。 1839年，30岁的达尔文与他的表妹爱玛结婚。爱玛是他舅舅的女儿。他们两人从小青梅竹马，感情深厚。但是，谁也没有料到，他们的6个孩子中竟然有3个夭亡。这件事情让达尔文百思不得其解，因为他和爱玛都是健康人，生理上没有什么缺陷，精神也非常正常，为什么生下的孩子却都是如此呢？达尔文到了晚年，在研究植物的生物进化过程时发现，异花传粉的个体比自花传粉的个体，结出的果实又大又多，而且自花传粉的个体非常容易被大自然淘汰。这时，达尔文才恍然大悟：大自然讨厌近亲结婚。达尔文意识到自己婚姻的悲剧在于近亲，所以他把这个深刻的教训写进了自己的论文。
材料二：
科学家将男、女体细胞内的染色体进行分析整理，形成了下面的排序图。

请分析材料回答下列问题：
⑴材料一中，从达尔文婚姻的悲剧可以看出，____ 是预防遗传病发生的有效措施。
⑵达尔文体细胞染色体的组成是材料二中的____  图。
⑶若材料二中的排序图表示的是电视剧《鲜花朵朵》中七个女儿父母的染色体组成，假如他们再生一胎，是男孩的可能性为____ 。
⑷正常人的染色体数目是相对恒定的，这对生命活动的正常进行非常重要。如果人的体细胞中多了或少了一条染色体，可能导致严重的____ 。