Height is just one of the thousands of features your genes (基因) decide. In fact, because you have two parents, your genes provide you a height that usually lands somewhere between the height of each parent. If both your parents are tall, then most probably you will be tall, too. If you have questions about how tall you're going to be, ask your doctor if he or she can help you find it out.

　 But genes don' t decide everything. For example, eating an unhealthy diet can keep you from growing to your full potential ( 潜力). Getting plenty of sleep and enough exercise will help you grow to the expected height.

　　 No doubt you' re wondering how fast you should grow. It depends. There' s no perfect or right answer, Generally speaking, kids grow about two inches ( six centimeters) a year between age three and the time when they start puberty.

　　 Your doctor will know how your growth has been going over the years. Two centimeters hero and two inches there are not nearly as important as the height you' re at now, how you' ve been growing up to this point, and what other changes your body may be going through.

　　 Don' t be nervous if you seem to have grown a lot in a very short time. Everyone has a growth spurt (高峰) during puberty. The age for starting puberty is about 10 for girls and about 11 for boys. But it can be earlier or later, between 7 and 13 for girls and 9 and 15 for boys.

　　 You'll usually begin to notice that you' re growing faster about a year or so after your body starts to show the first changes of puberty.　　　　　　　　　　　　　　　　　　　　　

根据短文内容，选择最佳答案，并在答题卡上按要求作答。

66. The underlined word “puberty” means 　　 in Chinese.

　　 A. 童年时期　　 B.婴幼儿时期　 C. 习惯养成期　 D.生长发育期

67. If you want to know how tall you shall grow,　　　　 .

　　 A. you should have enough exercise　 　B. you can ask your doctor for help

　　 C. you should have a healthy diet 　　　 D. yon can record your growth during puberty

68. After reading this passage, we can learn 　　　　　 .

　　 A. how good it is to be a doctor　　　　 B. how much sleep time we need

　　 C. why genes can't decide everything　　 D. what is a healthy diet for children

69. Which is NOT mentioned in the passage?

A. Your height most probably depends on how tall your parents are.

　 　B. Girls' age for staffing puberty is usually earlier than boys'.

　　 C. The time showing the first changes of puberty is never noticed.

　　 D. You may be nervous sometimes when you grow too fast.

70.This passage is mainly about __.

　　 A. how the genes work in your body 　　 B. "the times at which you grow the most

　　 C. how you grow during your puberty ,　 D. how you grow to a certain height