Step 1: Understand the question type.
We must find the statement that is wrong about heterolysis. So we should know clearly what heterolysis is and how it differs from homolysis.
Step 2: Recall heterolysis.
In heterolysis a covalent bond breaks unevenly. The more electron-pulling atom keeps BOTH shared electrons. This makes one part a negative ion (electron rich) and the other part a positive ion (electron deficient).
Step 3: Recall homolysis for contrast.
In homolysis the bond breaks evenly. Each atom takes just ONE electron, making neutral free radicals. So a single-electron move belongs to homolysis, not heterolysis.
Step 4: Test options A and C.
Option A says electron rich and electron deficient species form. This is true for heterolysis. Option C says it happens when the two atoms have different electronegativity. This is also true, because the stronger atom pulls the whole pair to itself.
Step 5: Test option B.
Option B says heterolysis of methyl bromide gives a methyl carbocation. Bromine is much more electron-pulling than carbon, so it takes the pair and leaves $\text{CH}_3^+$ and $\text{Br}^-$. This is true.
Step 6: Spot the wrong one.
Option D says a single electron moves from the shared pair. That describes homolysis, not heterolysis. In heterolysis the whole pair (two electrons) moves together. So option D is the wrong statement, and that is our answer.
\[ \boxed{\text{Option D}} \]