The correct answer is option 4, electromagnetic waves.

Gamma rays, also known as y-rays, are a type of electromagnetic radiation. They have the shortest wavelength and highest energy among the electromagnetic spectrum.

Option 1, meson particles, is incorrect. Mesons are particles composed of a quark and an antiquark, and they do not fall under the category of gamma rays.

Option 2, neutrino particles, is incorrect. Neutrinos are elementary particles with a very small mass and negligible charge. They are not electromagnetic radiation like gamma rays.

Option 3, Higgs boson, is incorrect. The Higgs boson is an elementary particle in the Standard Model of particle physics, but it is not related to gamma rays or electromagnetic waves.

Gamma rays are produced through various processes, such as nuclear reactions, radioactive decay, and high-energy particle interactions. They are highly energetic and have various applications in medicine, industry, and research.