列式并计算．

C

    Do you have brown hair? Are you taller than other kids your age? These characteristics were decided before you were born. You got your traits from your parents. They passed their traits on to you through genes (基因).

    Genes carry codes (代码) for blue eyes or brown eyes. Genes say how tall you will get and what color hair you will have. You got half of your genes from your mother. You got half of your genes from your father. So you have your own set of genes. Each person gets different genes for each body part. That is why you look like but not exactly like your brother or sister.

    A dominant (显性的)  gene shows up most of the time. Brown eyes are dominant over bluc eyes. A recessive (降性的)  gene shows up less often. Light hair comes from a recessive gene. Dark hair is more common. Look at the eye color and hair color of the people around you. You will see that this is true.

    Genes help to make you who you are. But they don't tell the whole story. Your genes may help you to be fast and strong. But you still need to learn how to run or swim or skate well.

已知平面向量$\overrightarrow{a}=\left(1,2\right),\overrightarrow{a}·\overrightarrow{b}=10,\left|\overrightarrow{a}+\overrightarrow{b}\right|=5\sqrt{3}$,则$\left|\overrightarrow{b}\right|$=（  ）

质点做直线运动的速度—时间图象如图所示，该质点（   ）

2016年9月27日，港珠澳大桥主体桥梁正式贯通；预计2017年年底建成通车。港珠大桥是世界最长的跨海大桥，连起世界最具活力的经济区，对促进香港、澳门和珠江三角洲西岸地区经济的进一步发展具有重要战略意义，其设计建造技术先进，是中国从桥梁大国走向桥梁强国的里程碑之作。这体现了以下哲学道理（    ）

①人们能够建立有利于自身的联系

②应立足整体、统筹全局，实现发展

③人为事物的联系是科学技术的产物

④人们根据自身的需要可以建立事物新的联系