Whichofthefollowingplaysakeyroleinbodygrowthaccordingtothetext？
A．Geneticmodification.
B．Naturalenvironment.
C．Livingstandards.
D．Dailyexercise.
正确答案：C从第三段“butasdietandhealthimproved,childrenandadolescentshaveincreasedinheightby…..”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geneticmodification,naturalenvironment和dailyexercise文中并没有提到。
