listEning 6 "BotAnyClAss"
{$mEDiAurl}

why DoEs thE proFEssor tAlk ABout thE history oF hyDroponiCs
A、shE wAnts to put thE moDErn mEthoD in historiCAl ContExt.
B、shE is trying to provE thAt hyDroponiCs is A nEw iDEA、
C、shE is Following thE inFormAtion in thE tExtBook vEry ClosEly.
D、shE DigrEssED From thE suBjECt For A long timE.