Anna is to work out the math problems and gets a good grade.A. hard enoughB. enough hardC

问题补充：

Anna is to work out the math problems and gets a good grade.

A. hard enough

B. enough hard

C. hard-working enough

D. enough hard-working

答案：

A. hard enough

B. enough hard

(答案→)C. hard-working enough

D. enough hard-working

解析：hard艰难的，困难的；hard-working勤奋的，勤勉的。句意：为了解决这道数学题，安娜足够努力了，并且获得了很好的分数。Enough做修饰词，修饰形容词时，一般要放在被修饰词后面，结合语境可知选C。