4) Heres some vague details (IE not listing specific lines or anything, but stating where OSIs are required.) of how to get to the London Airports (Stansted, T**twick, Heathrow, London City and Luton) by rail (including DLR and Underground). I'm not saying which airport is which. These are for the simplest way, that is, the way with least changes. Where there is multiple ways with equal changes to get to an airport, I'm choosing the cheapest way. For this clue, consider only services that run 10:00 - 15:00 M-F.
Airport 1) NR (Northbound), NR, OSI, NR.
Airport 2) NR (Southbound), DLR
Airport 3) NR (Southbound), LU, NR.
Airport 4) NR (Either way), LU, LU.
Airport 5) NR (Southbound), NR
For airport 1, fewer changes are required if you use a different station within one mile of this one (by foot, distance is based on recommended route on Google Maps)