“情态动词+have+过去分词”也可称为“情态动词+不定式完成体”.由于初学者对其意义和用法缺乏深刻的理解,往往很难对这种结构作出正确的判断.现将它们分述如下:一、“must+have+过去分词”表示对过去发生的动作的推测.意为“一定(准是、肯定)已经……”,只限用于肯定句.如:Where is my pen?I must have lost it.(’83MET) “Modal verb +have+past participle” can also be called “modal verb + infinitive complete body”. Because beginners lack a deep understanding of their meaning and usage, it is often difficult to make correct judgments on this structure. Now they are Divide as follows: First, “must+have+ past participle” means to speculate on actions that happened in the past. It means “certain (probably, definitely) already...” and is used only for affirmative sentences. For example: Where is my pen ?I must have lost it.(’83MET)