Воткните глагол tobe в Present , Past или Future Simple.1) He__in

1) He will be in St. Petersburg tomorrow.

2) Where are your books now? They are in my bag.

The first sentence is in Future Indefinite. Future Indefinite is formed with the help of the auxiliary verb will. The keyword of future Indefinite is tomorrow.

The second sentence is in Present Indefinite. The present forms of the auxiliary verb to be are am(for the first person singular), is (for the third person singular) and are (for all the persons plural). Your books is the third person plural and they is the third person singular. Thats why we use are.