The math problem is difficult that only students can work it out.A. too; a fewB. so; a f

问题补充：

The math problem is difficult that only students can work it out.

A. too; a few

B. so; a few

C. so; a little

D. enough; little

答案：

A. too; a few

(答案→)B. so; a few

C. so; a little

D. enough; little

解析：too太,也;so如此,这么;enough足够的;a few几个,修饰可数名词复数;a little一点,修饰不可数名词;little一点,表示否定含义;句意:这道数学题有点难,以至于只有几个学生能计算出来.结合语境可知选B.