Which one should I use in each case?
Can I use both when it's a little unclear which one to use?
?1?
W: You may need a ticket.
M: "Actually, I do have one (a ticket)" or “Actually, I do have it (the ticket)”?
If the man interprets a ticket as one out of many tickets, he’ll use one (a ticket).
But if he interprets a ticket as one certain ticket, he’ll use it (the ticket).
?2?
In an airline announcement,
“We are now making a final approach” or “We are now making the final approach”?
I think the adjective final is a word that can refer to something that is unique.
I think you understand both correctly. The use of 'one' suggest 'one of the possible tickets' but at the same time we know implicitly that it is a ticket that is relevant to a particular journey. Using 'it' suggests that there is only one possible ticket that would be appropriate.
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I think you understand both correctly.
The use of 'one' suggest 'one of the possible tickets' but at the same time we know implicitly that it is a ticket that is relevant to a particular journey. Using 'it' suggests that there is only one possible ticket that would be appropriate.
The 'final approach' is a one-off and therefore needs 'the'.