Select the most appropriate option to fill in the blank.
Tickets for the event are available ______ the door; there is no advance booking.

Correct option is A

The correct option to fill in the blank is (a) "at".
Explanation:
The phrase "at the door" is a standard English phrase used to indicate that something (such as a ticket) is available for purchase or collection at the entrance of a venue.
Example:
✅ You can buy tickets at the door before the show starts.
❌ You can buy tickets in the door before the show starts.
Why Other Options Are Incorrect:
· (b) "in" – Incorrect, because "in" is used for enclosed spaces, whereas the door is a point of entrance.
· (c) "of" – Incorrect, because "of the door" does not convey the correct meaning.
· (d) "to" – Incorrect, because "to the door" implies movement towards the door, not availability at the door.