Нужно употребить во в косвенной речи
He doesn't know (Who was the nineteenth president of the United States?). He isn't sure (When did the Civil War end?), He doesn't remember (When did California become a state?), He has forgotten (Where was George Washington born?). He can't remember (How many people signed the Declaration of independence?). He doesn't know (Where was Abraham Lincoln assassinated?). He has forgotten (Why was Washington chosen as the capital?). And he has no idea (What did Alexander Graham Bell invent?).

I like spring very much. When I have my holidays in spring I enjoy myself. It is very great to have holidays in spring. To begin with I shall walk with my friends if the sun shines brightly in the sky. I enjoy the blue sky and even spring rain. The spring rain is warm and pleasant. I shall watch fresh leaves and blossoms on the trees. I feel stronger and kinder in spring. Secondly I can go to countryside and have a walk in a forest or by a river with my best friend in spring. We enjoy playing ballgames. Sometimes we can lie in the sun and watch the clouds. Sometimes we can swim in a river if the water is warm enough. And at last if you do not like nature you can play your computer and enjoy your free holiday time.

I like spring very much. When I have my holidays in spring I enjoy myself. It is very great to have holidays in spring. To begin with I shall walk with my friends if the sun shines brightly in the sky. I enjoy the blue sky and even spring rain. The spring rain is warm and pleasant. I shall watch fresh leaves and blossoms on the trees. I feel stronger and kinder in spring. Secondly I can go to countryside and have a walk in a forest or by a river with my best friend in spring. We enjoy playing ballgames. Sometimes we can lie in the sun and watch the clouds. Sometimes we can swim in a river if the water is warm enough. And at last if you do not like nature you can play your computer and enjoy your free holiday time.