A:斓语力挽狂澜荟萃鞠躬尽粹
B:阴晦诲人不倦耸峙恃才放旷
C:必需锋芒必露抵挡锐不可当
D:契约锲而不舍鉴定油光可见
— What;s the matter?
— I am having trouble ______ who has taken my book.
唐朝长安城内繁华的商业区叫做( )