$\begin{array}{1 1} \text{a.electrostatic repulsion between α particles and positively charged part of atom} \\ \text{
b. electrostatic attraction between α particles and positively charged part of atom} \\ \text{
c. electrostatic repulsion between β particles and positively charged part of atom} \\
\text{d. electrostatic attraction between γ particles and positively charged part of atom
}
\end{array} $
