I usually get to work on foot and then come home on the bus.
It refers to a system or service.
The universe is nearly 14 billion years old.
There's only one.
The dove is a symbol of peace in many different cultures.
It refers to a whole group of things.
I wish I could play the piano.
It refers to a musical instrument.
Simon is probably the best rugby player in the county.
It's with a superlative adjective.
Excuse me, where's the bathroom?
There's only one in the context.
A: I'm reading a great book at the moment.
B: Really? What's the book about?
It's been mentioned already.
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