London is a key test-bed for the UK hydrogen economy and also on Tuesday, the city took delivery of a dozen new zero-emission vehicles from Toyota , powered by hydrogen fuel cells made by UK-based ITM Power (LSE: ITM.L - news ) , while Mayor of London Boris Johnson also timed a visit to the Japanese headquarters of the car manufacturer on the same day.
Utilize the input text as a context reference, choose the right relationship between 'Boris Johnson' and 'Mayor of London' from the options.
Options: position held, location of formation, distributed by, stock exchange