—If you want to sell your old house, why not put an _____in the newspaper?            

—Good idea.       [ ]

A. e-mail            

B. advertisement      

C. article            

D. advice

有一个天平，九个砝码，其中一个砝码比另八个要轻一些，问至少要称几次才能将轻的那个找出来？