We walked back about two____(千米)and found Sam at last.
①CH3CH═CH2+Br2→CH3CHBrCH2Br
②CH3CH2OH →△浓H2SO4 CH2═CH2↑+H2O
③CH3COOH+CH3CH2OH →△浓H2SO4 CH3COOCH2CH3+H2O
④C6H6+HNO3 →△浓H2SO4 C6H5NO2+H2O.
①实施乡村振兴战略 ②改革收入制度,实现均等分配
③加强生态文明建设 ④外来务工人员随迁子女在流入地接受义务教育