$\begin{array}{1 1} \text{a. The force of attraction exerted on α particles by the electrons is insufficient } \\ \text{
b. The volume of nucleus is much smaller than that of the atom} \\ \text{
c. The force of repulsion acting on the fast moving α particles is very small } \\ \text{
d. The neutrons have no effect on α particles}
\end{array} $
