The students busily, when we up to them. *

Отрицательная форма:
1) She didn't understand us. [Время
2) They don't teach them. [Время - Настоящее]
3) We will not make a doll. [Время - Будущее]

Вопросительная форма:
1) Did she understand us? [Время
2) Do they teach them? [Время - Настоящее]
3) Will we make a doll? [Время - Будущее]

Положительная форма:
1) She understood us. [Время
2) They teach them. [Время - Настоящее]
3) We will make a doll. [Время - Будущее]

P.S: курсивом выделил неправильные глаголы.
Формы глаголов:  understand - understood - understood
teach - taught - taught
make - made - made

1.
Had we finished the project by Sunday?
What had we finished by Sunday?
Had we finished the project or the article by Sunday?
We had finished the project by Sunday,hadn't we?
Who had finished the project by Sunday?
2.
Will they go to Paris next year?
Where will they go next year?
Will they go to Paris next month or next year?
They will go to Paris next year,won't they?
Who will go to Paris next year?
3.
Does she help her mother every day?
When does she help her mother?
Does she help her mother every day or every week?
She helps her mother every day,doesn't she?
Who helps her mother every day?
4.
Are children playing in the garden now?
Where are children playing now?
Are children playing in the garden or in the yard now?
Children are playing in the garden now,aren't they?
Who is playing in the garden now?
5.
Didn't my friend write a letter yesterday?
What didn't my friend write yesterday?
Didn't my friend or my sister write a letter yesterday?
My friend didn't write a letter yesterday,did she?
Who didn't write a letter yesterday?