________respect, ________yourselves to ______high grades is the best way.

A．To earn, devote, achieving

B．Earn, devoting, achieve

C．To earn, devoting, achieving

D．Earning, devote, achieve

在一块长12m，宽8m的长方形平地中央，划出地方砌一个面积为8m²的长方形花台，要使花坛四周的宽地宽度一样，则这个宽度为多少？