Question

Поставьте эти предложения в отрицательную форму There is a bookshelf by the window

Answer 1

There is not a bookshelf by the window

Answer 2

There is not a bookshelf by the window.
если сокращенно то, isn't

Answer 3

In the negative form, the sentence "There is a bookshelf by the window" would be:

"There is no bookshelf by the window."