Height is just one of the thousands of features that 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 maybe 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 your full potential (潜力). Getting enough sleep and enough exercise will help you grow to the right height.
Maybe you’re wondering how fast you should grow. There’s no right answer. Kids grow about 2 inches (5 centimeters) a year between age 3 and the time they start puberty（青春期） .
Your doctor will know how your growth (生长) has been going over the years. Two centimeters here and 2 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 worried if you have grown a lot in a very short time. Everyone has a very quick growth 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, 9 and 15 for boys.
You’ll usually begin to find that you’re growing faster about a year after your body starts to show the first changes of puberty.
If you want to know how fast and how tall you should grow, _______.

A．you should have enough exercise

B．you can ask doctors for help

C．you should protect the environment

D．you can record your growth during puberty

This passage is mainly about _______.

A．how the genes work in your body

B．when the time you grow fast is

C．why you look like your parents

D．how you grow to a certain (某一) height

After reading this passage, we can explain (解释) _______.

A．how good it is to be a doctor

B．how much sleep we need

C．why genes can’t decide everything

D．what an unhealthy diet is