Playing on a frozen sports field sounds like a lot of fun. Isn't it rather risky, ________?[ ]

A. though  

B. also

C. either  

D. too

按货物运输条件不同可以将货物分为普通货物和( )。

A．特种货物
B．大型货物
C．轻泡货物
D．堆积货物