A：一般动物吃不到较高处的树叶，但脖子较长的长颈鹿却能吃到，因此有生存优势，能留下更多的后代
B：在求偶季节，雄长颈鹿会挥动长脖子互相撞头进行决斗，脖子越长，就越容易获胜，取得更多的交配机会
C：长颈鹿生活在土壤贫瘠的非洲内地，因此它不得不尽力伸长脖子去吃树叶，这导致它脖子变得较长
D：长颈鹿种群中脖子普遍很长，其根本原因是与长脖子相关的基因频率的提高
—Which of the two cameras are you going to buy?
— I'll buy______ of them because I want to give one to my best friend.
若平面α与β的法向量分别是a→=（1，0，﹣2），b→=（﹣1，0，2），则平面α与β的位置关系是（ ）
Many teenagers feel that the most important people in their lives are their friends．They believe that their family members don’t know them as well as their friends do．In large families，it is quite often for brothers and sisters to fight with each other and then they can only go to their friends for some ideas． It is very important for teenagers to have one good friend or a group of friends．Even when they are not with their friends，they usually spend a lot of time talking among themselves on the phone．This communication is very important in children’s growing up，because friends can discuss something．These things are difficult to tell their family members． However，parents often try to choose their children’s friends for them．Some parents may even stop their children from meeting their good friends．Have you ever thought of the following questions? Who chooses your friends? Do you choose your friends or your friends choose you? Have you got a good friend your parents don’t like? Your answers are welcome．
