Only when class began ______that he had left his book at home．

A．will he realize

B．he did realize

C．did he realize

D．had he realized

我国税收是新型的税收，它“新”在（）

A.我国税收的主体是人民群众

B.我国税收是取之于民

C.我国税收是为广大劳动人民服务的

D.我国税收是为国家实现其职能服务的