下列情况，可以用红字记账的有( )。

A．在不设借贷等栏的多栏式账页中，登记减少数

B．在三栏式账户的余额栏前，如果未标明余额方向的，在余额栏内登记增加数

C．按照红字冲账的记账凭证，冲销错误记录

D．冲销账簿中多记录的金额

The question that puzzled them is ____ they can get rid of the air pollution in the area.

A．how is it that

B．that how

C．that it is how

D．how it is that