What could the Extremely Large Telescope see at Proxima Centauri's planet?

Proxima Centauri B is the closest exoplanet to Earth. It is an Earth-mass world right in the habitable zone of a red dwarf star just 4 light-years from Earth. It receives about 65% of the energy Earth gets from the sun, and depending on its evolutionary history could have oceans of water and an atmosphere rich with oxygen.