Question: About free radicals: 
 Options:  <1> They are compounds that contain two or three unpaired electrons in an outer orbital. <2> Reactive oxygen species (ROS) in the cell are only generated enzymatically. <3> Hydrogen peroxide is the most damaging radical in the cell. <4> The hydroxyl radical originates non-enzymatically (Heber-Weiss reaction) and damages proteins and DNA. <5> Oxygen is a triradical.
4