PLS HELP ITS FOR MY EATH SCIENCE CLASS?!?!

Our closest exoplanet and Earth-sized planet is Proxima Centauri b.
Proxima Centauri b is in the habitable zone, but why is it not a suitable
Earth 2.0?

A enormous amounts of radiation from mega flares hit the planet
roughly once every year

B it lacks an atmosphere, therefore most likely lacks water

C extreme temperature changes on the surface

D all of the above