Iwouldhavecomesooner____possible,butI____thatyourwerestillwaitingforme.A.itwere...didn'tkonwB.wereit...hadn'tknowC.ithadbeen..wouldn'thaveknownD.haditbeen...didn'tknow.答案是选D.希望可以解释一下这句话的意思.

　　Iwouldhavecomesooner____possible,butI____thatyourwerestillwaitingforme.

　　A.itwere...didn'tkonw

　　B.wereit...hadn'tknow

　　C.ithadbeen..wouldn'thaveknown

　　D.haditbeen...didn'tknow.

　　答案是选D.

　　希望可以解释一下这句话的意思..和为什么选D...