过去HaddoneWould*havedone
现在Were/didWould*do
将来Shoulddo/were/weretodoWould*do
例句:Iftherehadn’tbeenmuchraininspring,wewouldhavehadagoodharvestnow.[过去]
Ifhesmokedless,hiscoughmightbewellsoon.[现在]
Ifthelecturershouldbelate,youwouldhavetomakeaspeechfirst.[将来]
主动:Wemustkeepthisinmind.
被动:Thismustbekeptinmind.
我们必须把这个记在心里.