__________ difficult the task may be, we will try our best to complete it in time.

A．Whatever

B．No wonder

C．Though

D．However

张某在甲地临时从事收购废品的业务，税务机关对其应采取的税款征收方式应当是( )。

A．代扣代缴

B．查定征收

C．代收代缴

D．核定征收