When ______ different cultures，we often pay attention only to the differences without noticing the many similarities.

A．compared

B．being compared

C．comparing

D．having compared

碳化塔中段气的进气位置应适宜，如位置过高，虽然结晶多，但是尾气中（）会相应增大。

A、氨

B、二氧化碳

C、回卤

D、氧