可以由that,sothat,inorderthat,lest,forfearthat,incase等词引导;
lest:以防;从句中的谓语动词必须用should+动词原形;
eg:Hewrotethenamedownforfearthat(lest)heshouldforgetit.
Hetooktheumbrellawithhimlestitshouldrain.
incase:以防;与lest不同,从句里的时态不做特殊变化;
eg:Taketheumbrellawithyouincaseitrains.
eg:Avarietyofactivitiesshouldbeorganizedsothatparticipantscanremainactiveaslongastheywantandthengoontosomethingelsewithoutfeelingguiltyandwithoutlettingtheotherparticipantsdown.