Step 1: Interpreting the given statement.
The statement “Mangoes are delicious but expensive” can be written logically as:
\[
p \land q
\]
where $p$: Mangoes are delicious, and $q$: Mangoes are expensive.
Step 2: Understanding the concept of duality.
The dual of a statement is obtained by interchanging logical AND ($\land$) with logical OR ($\lor$), without negating the propositions.
Step 3: Writing the dual statement.
The dual of $p \land q$ is
\[
p \lor q
\]
That is, “Mangoes are delicious or Mangoes are expensive.”
Step 4: Conclusion.
Hence, the correct dual statement is option (C).