complete the sentences.1.this is a bookcase.-These are...2.That......a window.-Those....windows.3.This is a door.-.....are....4.That is a chair.-....are.....5..........Ara blackboard.-These are.....6......is a table.-Those...........

1. These are bookcases.
2. That is a window.- Those are windows.
3. This is a door. - These are doors.
4 That is a chair. - Those are chairs. 
5. This is a blackboard. - These are blackboards.
6That is a table. - Those are tables.