Given an trivia question precisely answer the question with a word/phrase/name. External resources such as Wikipedia could be used to obtain the facts.

The American television series 'The Lone Gunmen', which centred on a group of investigators who ran a conspiracy theory magazine, was a spin-off of which other succesful series?
the x-files

Whose opera La gazza ladra premiered in 1817?
gioachino rossini

In which English city is the HQ of the Ordnance Survey?

southampton