成交额和客户数分别占本公司总额的70%和10%左右的是( )。
A．A类客户
B．B类客户
C．C类客户
D．D类客户
参考答案：A
有关声束远场，下列正确的是（）。
A.远场声束呈圆柱形
B.远场区能量分布不均匀
C.随距离扩散
D.不受吸收衰减的影响
E.扩散角愈小，声束扩散愈大
Working independently, Tina can do a certain job in 12 hours. Working independently, Ann can do the same job in 9 hours. If Tina works independently at the job for 8 hours and then Ann works independently, how many hours will it take Ann to complete the remainder of the job ？（）
A.A
B.B
C.C
D.D
E.E
