贝多芬作品的特点是

①构思广阔 ②形式宏大 ③洋溢着英雄主义和乐观主义精神 ④蕴涵着哲理[ ]

A．①②④   

B．①②③    

C．①②③④   

D．②③④

Last term our maths teacher set so difficult an examination problem _____ none of us worked out.

A．that

B．as

C．so that

D．which