A:CH2=CH2+H2 →催化剂 CH3-CH3
B:CH3CH2OH+3O2 →点燃 2CO2+3H2O
C:
D:CH4+Cl2 →光 CH3Cl+HCl
He never ____learning English .That was why he was successful at last.
The doctor advises me to take the medicine t____ a day, in the morning and evening.
在我国,“志愿者”已越来越被公众所认可。据有关机构进行的一项社会调查显示:97.6%的青年表示“有空的时候,愿意去做公益活动的志愿者。”志愿者的行为是( )