Step 1: Understand what is asked:
The question asks for the document that an airline issues to let a passenger board a particular flight.
The key idea is permission to travel on one specific flight, on one date, in one seat.
Step 2: Recall the travel documents:
After check-in, the airline gives the passenger a boarding pass.
It shows the passenger's name, flight number, date, seat number, gate and boarding time.
Security staff and the cabin crew check it before the passenger enters the aircraft.
Step 3: Why the other options are wrong:
Passport: it is an identity and nationality document issued by the Government of India, not by an airline.
Itinerary: it is only a schedule of the journey, listing flights, dates and halts. It gives no permission to board.
Travel Insurance Policy: it is a contract with an insurer that covers risks like loss of baggage or medical cost. It does not allow boarding.
Final Answer:
The document issued by an airline that permits a passenger to board a flight is the Boarding Pass, which is option (A).