Excel for Kazakhstan grade 6 Workbook& Grammar Book страница 49

1.while she was playing the piano, I was writing a letter.2.he was going  to the university, when i met her.3.Our friends were  discussing something when we interrupted them.4.My mother was  watching TV, when I came into the room.5.I haven't seen him since he  moved to his newflat.6.When I was looking out of the window, I saw that it was raining hard and people were  hurrying along the street.7.We were leaving the  house, when the telephone rang.8.I was sitting on the river bank , when my friends joined me.9.When I came up to him, he was speaking to his friends.10.We met her when she was walking home.11.When she  entered the room ,I was standing at the window.12.When we  entered the room he was  smoking  and  speaking to his friends.13.I was watching TV when somebody knocked at the door.14.What were you  doing ,when I rang you up yesterday?15.Her son was cooking dinner, when she came home. 16.She was  watering the flowers, while her husband was watching TV  

Глагол to be может быть глаголом-связкой в именном сказуемом (в значении "есть").Формы глагола to beI am-я есть (существую) He / She / It is-он, она, оно есть (существует) We are-мы есть (существуем) You are-ты, вы есть (существуете) Тhey are-они есть (существуют)
глагол to be может быть глаголом-связкой в именном сказуемом (в значении "есть").-I am a doctor.Я врач. (Я есть врач.)
Чтобы задать вопрос нужно поставить глагол to be перед подлежащим:Am I happy?
Для образования отрицательной формы достаточно поставить отрицательную частицу not после глагола to be:I am not happy.