Which of the following plays a key role in body growth according to the text?

参考答案:

C从第三段“but as diet and health improved, children and adolescents have increased in height by…..”可以看出生活水平对于身体成长起着非常重要的作用;另外，A，B，D选项所涉及的genetic modification ,natural environment 和daily exercise文中并没有提到。