The rate-limiting step of an $S_N1$ reaction follows the sequence shown below. Based on the assumption that $R$ contains $3$ different groups,which statement is true?
$\mathop R\limits^{\delta \oplus } \,\mathop {Br}\limits^{\delta \Theta } \, \rightleftharpoons \,\mathop {\boxed{{R^ \oplus }Br^\Theta }}\limits_{(a)} \,\,\, \rightleftharpoons \,\mathop {\boxed{{R^ \oplus }}\,\boxed{Br^\Theta }\,}\limits_{(b)} \,\, \rightleftharpoons $ ${\boxed{{R^ \oplus }}}$ $ + $ $\mathop {\,\boxed{Br^\Theta }\,}\limits_{(c)} \,$

• A
  The more stable the carbocation,the greater the proportion of racemization.
• B
  The more nucleophilic the solvent,the greater the proportion of inversion.
• C
  In the above sequence,$(b)$ represents separately solvated ion pairs.
• D
  All of these.