现在完成时是英语中描述过去对现在影响的时态,由助动词“have”或“has”和过去分词构成。"Have"用于第一、二人称单数和复数,而"Has"用于第三人称单数。现在完成时常与时间状语连用,可以是具体或不确定的时间。使用现在完成时时,需要注意动词的过去分词形式,包括规则动词和不规则动词。
“Have”用于第一人称单数(I)、第二人称单数(you)、第一人称复数(we)和第二人称复数(you)。
例如:
- I have studied English for 5 years.
- You have eaten breakfast already.
- We have finished the project on time.
- You have traveled to many countries.
“Has”用于第三人称单数(he、she、it)。
例如:
- He has worked in this company for 10 years.
- She has written a book.
- It has rained all day.
需要注意的是,现在完成时常与时间状语连用。时间状语可以是具体的时间,如“yesterday”、“last week”,也可以是不确定的时间,如“ever”、“never”、“already”、“yet”等。
例如:
- I have visited Paris twice.
- Have you ever tried sushi?
- He has not finished his homework yet.
- They have already seen the movie.
在使用现在完成时时,我们需要注意动词的过去分词形式。过去分词是动词的第三个形式,通常由动词加上-ed结尾构成。但是也有不规则动词,需要记住它们的过去分词形式。
例如:
- study - studied
- eat - eaten
- finish - finished
- write - written
- work - worked