现在完成时

　　一、现在完成时的构成式是have（has）＋动词的?ED分词。

　　1）Research ［A］in molecular（分子的）biology has demonstrate ［B］phenomenal similarities ［C］between ［D］humans and apes（类人猿）。

　　2）Gore Vidal has steadily pursue ［A］ a literary career ［B］remarkable ［C］for its productivity，versatility（多样性） and unpredictability ［D］ （多变性）。

　　3）For centuries large communities of people have living ［A］on houseboats in parts ［B］of the world where ［C］the climate is warm and the waters are calm ［D］。

　　二、现在完成时表示到现在为止的一段时间内发生的情况或动作，强调的是对现在的影响，可能是已完成的动作，也可表示多次动作的总和，或习惯性的行为和持续的动作。

　　4）Ninety eight percent of all animal species ［A］in ［B］history had ［C］died out ［D］.

　　5）The domestic ［A］dog，considered to be the first tamed animal，is coexisting ［B］with human beings since ［C］the days of the cave dwellers ［D］（居住者）。

　　三、如果句中有表示到现在为止这段时间的状语时，用现在完成时，这些时间状语有now，today， this week，this month，this year，现在完成时不和表示具体的时间状语连用，如yesterday，last year等，但可以和always，before， just，in／during the past（few weeks，years，fifty years）连用，这时in表示"过去多少时间"，不能用after。

　　6）Industrial ［A］management is the aspect ［B］of business ［C］management that was ［D］most prominent in the United States in the past eight years.

　　7）Learning a foreign language is especially ［A］difficult for those ［B］who had ［C］never learned one before ［D］.

　　四、在有already，as yet，yet，ever，just，never 这类副词作状语的情况下，用现在完成时。

　　8）In just ［A］the last ［B］few years，football is become ［C］more popular than baseball in that country ［D］.