Which airfield is associated with the Chinook helicopter?

The correct choice is associated with the Chinook helicopter because Odiham is the primary base for the UK's Chinook fleet. Located in Hampshire, it serves as a key operational and training site for the Royal Air Force's Chinook operations. The base plays a vital role in supporting various flights, including transport and logistics missions, particularly in conflict zones or humanitarian efforts.

The other locations mentioned, while they may support different aviation operations or aircraft types, do not primarily serve the Chinook helicopters. Northolt is primarily a light aircraft airport used mainly for VIP and military transport. Valleg does not hold significance in the context of the Chinook fleet within the UK. Mount Pleasant, located in the Falkland Islands, primarily supports the British military presence there and does not serve as a main base for the Chinook helicopters. Thus, Odiham stands out as the clear and correct association for the Chinook helicopter operations within the Royal Air Force.