The director’s new film turned out to be ____ failure, but as we know, success often comes after _____failure.

A．a; a

B．x; x

C．a; x

D．x; a

商家对其新鲜葡萄进行减价促销活动，规定每天比前一天减价20%，某人在出售的第二天买了3千克。在出售的第三天又买了5千克，两次共花了42元，问如果这8千克葡萄都在第四天买只要( )

A．30.72元

B．31.64元

C．31.84元

D．32.08元