Present Perfect 1) Wealready this book ( read)
2) They the accident. They were at school. ( see)
3) Lilian her homework? lt seems she didn'l (do)

1) We have already read this book.
2) They have seen the accident. They were at school
3) Have Lilian done her homework? It seems she didn’t.

1) We have already read this book.
To form the Present Perfect tense, we use the auxiliary verb "have" followed by the past participle of the main verb. In this case, the main verb is "read" which becomes the past participle "read." Since the action of reading the book is completed in the past, we use "have" to indicate that the action happened before now.

2) They have seen the accident. They were at school.
Similarly, to form the Present Perfect tense, we use the auxiliary verb "have" followed by the past participle of the main verb. In this case, the main verb is "see" which becomes the past participle "seen." Since the action of seeing the accident is completed in the past, we use "have" to indicate that the action happened before now.

3) Lilian hasn't done her homework. It seems she didn't do it.
To form the negative of the Present Perfect tense, we add "not" after "have" to create "haven't." The main verb "do" becomes the past participle "done." Since Lilian didn't finish her homework, we use the negative form of the Present Perfect tense to indicate that the action didn't happen before now.

It is important to note that the Present Perfect tense is used to talk about past experiences or actions that have a connection to the present moment, or to indicate that something was completed before now.