Make tag questions and answer them london is the biggest city , isn't

the kremlin itslef wasn't called the fire. that was the name of the red square until 17th century because of numerous cases of fire that took place in and near kremlin and other neighbour buildings.

to do a crossword 

a crossword is done

is a crosswod done?

a crossword is not done

to read a book

a book is read

is a book read?

is  the book written?  

a book is not read

to recite a poem

a poem is recited

is a poem recited?

если надо поменять время, то принцип тот же