The rest mass of the Higgs boson is estimated to be close to 100 GeV. The Higgs boson was discovered at CERN’s Large Hadron Collider (LHC) in 2012. Experimental measurements determined its mass to be approximately 125 GeV/c². Of the given options, 100 GeV is the closest value. MeV (Mega-electronvolt) and GeV (Giga-electronvolt) are units of energy commonly used in particle physics, where mass is often expressed using the mass-energy equivalence E=mc². 1 GeV = 1000 MeV. The given options represent masses in the range of MeV and GeV. 0.5 MeV is too small (closer to the mass of an electron), 900 MeV is closer to the mass of a proton or neutron, 100 GeV is in the correct ballpark for the Higgs boson, and 1000 GeV (1 TeV) is much higher.