下列条件中不能判断四边形ABCD为平行四边形的是[ ]

A.AB=CD，BC=DA

B.AB∥CD，AB=CD

C.AD∥BC，AB=CD

D.AD∥BC，∠B=∠D

Li Ming is ______ excellent student. He often gets to school ______ hour earlier than the other students.[ ]

A. an; an      

B. an; a    

C. a; the    

D. an; the