<prompt> Which of the following is not a free radical, but it is a reactive oxygen species?HydroxyradicalHydrogen peroxideSuperoxide radicalBoth 1 2  <response>: Most powerful oxygen free radical is Hydroxyradical.Least powerful Reactive Oxygen speciesROS is Hydrogen peroxide.Precursor of all Reactive Oxygen species is Superoxide radical.H2O2 is not a free radical, but a ROS.Reference- Review of biochemistry Pg-411 