Complete the sentences.1.this is a bookcase.-These are...2.That......a window.-Those....windows.3.This is a door.-.....are....4.That

1. This is a bookcase. — 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.6. That is a table. — Those are tables.