Premise: Green Day . For much of the group 's career , the band has been a trio with drummer Tré Cool , who replaced former drummer John Kiffmeyer in 1990 prior to the recording of the band 's second studio album , Kerplunk ( 1991 ) . John Kiffmeyer ( born July 11 , 1969 ) , known professionally in music as Al Sobrante , is an American musician , best known as the former drummer for the punk rock band Green Day .
Hypothesis: John Kiffmeyer is the former bassist for Green Day.
Label: CONTRADICTION