Concept:
Dual of a Boolean expression is obtained by:
• Replacing \(+\) with \(\cdot\)
• Replacing \(\cdot\) with \(+\)
• Constants 0 and 1 are interchanged (not needed here)
Step 1: Given expression
\[
A + B(AC) + D
\]
Step 2: Replace operations
\[
+ \rightarrow \cdot,\quad \cdot \rightarrow +
\]
Step 3: Apply transformation
\[
A \cdot [B + (A + C)] \cdot D
\]
Step 4: Simplify expression
\[
A(B + AC)D
\]
Step 5: Conclusion
\[
\boxed{A(B + AC)D}
\]
Final Answer:
\[
\boxed{(D)}
\]