----- What’s this?----- ____ a ruler.
There isn't ______ in the classroom. Let’s turn off the lights.
Something was wrong with my bike, ______ I was late for school.
—Where is your Chinese teacher?—He’s ______the meeting room.
—Who is that lovely girl?—______ is my sister.
—Excuse me, can you tell me ________?—Sorry, I’m a stranger here.