A neutron consists of one up ($u$) quark together with two down ($d$) quarks. If a neutron changes into a proton, a beta-particle is released. What change occurs in the neutron’s quark structure as a result of the emission of the beta-particle? (The symbol for a neutrino is $\nu_e$ and for an antineutrino is $\overline{\nu}_e$.)
- A$d \rightarrow u + \beta^- + \nu_e$
- B$d \rightarrow u + \beta^- + \overline{\nu}_e$
- C$u \rightarrow d + \beta^+ + \nu_e$
- D$u \rightarrow d + \beta^+ + \overline{\nu}_e$