2．去年“5．12”汶川地震，瞬间山崩屋塌，然而位于四川成都、历经二千多年的古代著名防洪灌溉水利工程未受损坏，它是                                     

A．郑国渠                                         B．都江堰    

C．灵渠                                             D．隋大运河?