индо-гангская неизменность это денудационная​

vjfyfhfvs: Объясните употребление времен группы Perfect, переведите.
1. This is a very good book, I have just read it with pleasure. 2. He has been absent this week. He has been ill. 3.1 haven't seen you for a long time. Where have you been all this time? 4. We haven't heard about her since 1989. 5. By the beginning of the lecture the laboratory assistant had brought all the necessary diagrams.

vjfyfhfvs: Помоги пожалуйста