下列反应属于加成反应的是( )
A:CH4+Cl2CH3Cl+HCl
B:CH2=CH2+HClCH3CH2Cl
C:2CH3CH2OH+O22CH3CHO+2H2O
D:2C6H6+15O212CO2+6H2O
He__________ school at 3 in the afternoon.