Red phosphorus is less reactive than white phosphorus because (a)the P—P bond length is greater in red phosphorus

White phosphorus Monomer (unstable due to angle strain) 7 P-BLOCK ELEMENTS (GROUP 15-18) Hence, we can see from the structure that red P has polymeric structure and the white P has monomeric structure. Thus, red P is less reactive in nature since it is more stable compared to white P which has high angle strain. Therefore, option (b) is the correct one.