— Credit cards are ________ useful when travelling.

— True. They save us the trouble of taking too much cash. [ ]

A. finally  

B. nearly

C. hardly  

D. particularly

下列物质的用途与其物理性质相关的是[ ]

A．金属铜作导线

B．氧气用于炼钢

C．氩气作保护气

D．天然气作燃料