Вопрос мне понятен это футбол , это книга. Какие предлоги поставить ?

Ответ:

1) What's this? It's a football. (ед. число)

2) What's this? It's a book. (ед. число)

3) What are these? They're cars. (мн. число)

4) What are these? They're clocks. (мн. число)

5) What's this? It's an apple. (ед. число, слово на гласную)

6) What's this? It's a camera. (ед. число)