7.1 The weak interaction is responsible for $\beta$ decay.
6.1 The quark model predicts the existence of baryons and mesons.
6.2 The quark model explains the hadronic spectrum.
9.1 The gauge group of QED is $U(1)$.
9.2 The gauge group of QCD is $SU(3)$.
1.3 The antiparticle of the electron $e^{-}$ is the positron $e^{+}$.