下列各组物质按单质、化合物、混合物顺序排列的是（　　）

A．氧气、水、白酒

B．天然气、煤、石油

C．水银、烧碱、纯碱

D．干冰、C₆₀、酒精

My brother is two metres in height. It's very difficult to find clothes big enough             him. [ ]

A. about

B. at

C. with

D. for