单项选择题
A.In streets. B.In airports. C.In subway stations. D.In concerts.
A.Sounds of 15,000 hertz. B.Sounds of 20,200 hertz. C.Sounds of 30,000 hertz. D.Sounds of 50,000 hertz.
A.see store clerks sitting around watching TV B.receive warm greetings from clerks C.show their respects to clerks D.be given a pamphlet introducing the goods