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．But 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 the expected height．But getting enough sleep and exercise will meet your need．

It s certain that you're wondering how fast you should grow．It depends．There's no perfect or right answer．Generally speaking，kids grow about 2 inches（6 cm）a year between age 3 and the time when they start adolescence．

Don't be scared if you seem to have grown a lot in a very short time．Everyone has a time to grow fastest during adolescence．The age for starting adolescence is about lo 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 adolescence．

1．What does the underlined word “adolescence” mean in Chinese?

A．嬰幼兒時期         B．童年時期             C．青春期                D．學生時期

2．If you want to know how fast and how tall you should grow，________．

A．you should eat a healthy diet                     B．you should have enough sleep

C．you can seek medical help from a doctor      D．you should have enough exercise

3．This passage is mainly about ________．

A．how the genes work in your body             B．how you grow to a certain height

C．when is the time you grow fast                   D．why you look like your parents

4．After reading this passage，we can explain ________．

A．what healthy diet is                                  B．how good it is to be a doctor

C．how much sleep time we need                     D．why genes can't decide everything

5．Which of the following sentences is NOT right according to the passage?

A．You．may be anxious sometimes when you grow too fast．

B．Boys' age for starting adolescence is usually later than that for girls'．

C．The time showing the first changes of adolescence is seldom noticed．

D．Your height most likely has something to do with how high your parents are．