Can you imagine what difficulty people had this year_______against the severe natural disasters?

A．fighting

B．to fight

C．fought

D．fight

用硅胶作吸附剂，薄层色谱法分离分析某极性物质，可采用的条件是（）

A.用低含水量的吸附剂

B.用强极性展开剂

C.用活性级别为Ⅰ级的吸附剂

D.用弱极性展开剂