现在完成时的构成
has + 过去分词-
have + 过去分词
eg：I have'n't seen you for a long time.
现在完成时的用法
- 表示迄今为止完成的事情
eg：He has already come. - 表示过去的事情对现在的影响
eg：I have broken up with my boyfriend. - 强调‘已经’完成的事情
eg：I have already been to Hangzhou.
eg：Have you been to Hangzhou yet? -
since与for
since+ 时间点
eg：I have been in Shanghai sice 2015.
for+ 时间段
eg：I have been in Shanghai for 4 years. -
主语 + be 动词 + the most + 形容词 + 名称 + 现在完成时表示迄今为止最...的
eg：It is the most amazing moive I've ever seen!
eg：Canon is the most beautiful music I have ever heard.
