Step 1: Recall the definition of potential difference.
Potential difference is defined as work done per unit charge:
\[
V = \frac{W}{q}
\]
Step 2: Identify the given values.
Work done:
\[
W = 12\,J
\]
Charge:
\[
q = 3\,C
\]
Step 3: Substitute into the formula.
\[
V = \frac{12}{3}
\]
Step 4: Perform the calculation.
\[
V = 4\,V
\]
Step 5: Interpret physically.
This means 4 joules of work is required to move 1 coulomb of charge between points A and B.
Step 6: Check units consistency.
\[
\text{Volt} = \frac{\text{Joule}}{\text{Coulomb}}
\]
So units are correct.
Step 7: Final conclusion.
Hence, the potential difference is:
\[
\boxed{4\,V}
\]
Therefore, the correct option is
\[
\boxed{(2)\ 4\,V}
\]