It's _____ problem _____ we can't work it out.[ ]

A. so confused a; that

B. such a confusing; that

C. such confusing a; so that

D. so a confused; so that

下列加点文言虚词的意义和用法都相同的一组是（ ）

A．不赂者以赂者丧作《师说》以贻之

B．其势弱于秦不拘于时

C．后人哀之而不鉴之蟹六跪而二螯

D．蚓无爪牙之利苟以天下之大