Magnetic fields cannot deflect

The correct answer is Option (4) → Gamma rays

A magnetic field deflects only charged particles, since the force is \( \vec{F} = q(\vec{v}\times\vec{B}) \), which is zero when \( q = 0 \).

Alpha rays (\( +2e \)), \( \beta^{+} \) rays (positrons, \( +e \)) and \( \beta^{-} \) rays (electrons, \( -e \)) are charged and are deflected. Gamma rays are high-energy photons with no charge, so they pass through a magnetic field undeflected.