吸附色谱法分离生物碱时，吸附剂一般选择氧化铝为宜；如选择硅胶，则需在碱性环境中分离，如在展开剂中加氨水、二乙胺等。（）
参考答案：对
___ comfortably in his armchair, the old man enjoyed the light music over the radio with his eyes half ___ .
A．Seating ; closed
B．Seated ; closed
C．Sitting ; close
D．Sat ; closing
什么是电弧的静特性？
