...度空间 关键词：原则与参数理论；第二语言习得；隐含pro参数；迁移 [gap=476]Key words: the Principles and Parameters theory, the Second Language Acquisition, the parameter of drop-pro, transfer ..
Althoughsecondlanguageacquisitionresearchesbased on thetheoryofprinciplesandparameters have arrived at different conclusions, the theory has provided useful researchmethods.