pp:动词的过去分词
现在完成时：have/has+been+pp
注意：hear/see/make sb (to) do sth
类似于这样子的短语主动语态时隐藏to,被动语态时要补一个to
现在完成时比较麻烦的就是关于延续性动词的问题,一般来说,当一样事情持续性发生时,就使用延续性动词.
比如：she borrows a book from me a month ago
现在完成时：she has kept a book from me for a month
借,这个动作不可能持续一个月,所以这里不能用borrow,而要用keep,保存的意思.
总结一下：这些词语是有延续性动词的,初中只要掌握这些,其他单词没有延续性动词.
buy-------have(has) had
borrow------have(has) kept
arrive--------have(has) been in/at
leave------have(has) been away
join------have(has) been in/a member of
die-------have(has) been dead
get married------have(has) been married
come/go-------have(has)been in/at
begin/start-------have(has) been on
stop------have(has）been over
如果有这些单词出现在句子中,就要考虑是否要用现在完成时
already ever for just never since yet recently