Concept:
Giorgione (c.1477--1510) was one of the leading painters of the Venetian Renaissance. His celebrated painting Sleeping Venus, begun around 1508--1510, remained unfinished at the time of his death.
The unfinished portions, especially the landscape and drapery, were completed by Titian (Tiziano Vecellio), not Tintoretto. Although Titian completed parts of the work, the overall conception and style remain distinctly Giorgione's.
Step 1: Examine Assertion (A).
Historical evidence confirms that Giorgione died before completing the painting.
\[
\boxed{\text{Assertion (A) is Correct}}
\]
Step 2: Examine Reason (R).
The statement is incorrect because the painting was completed by
\[
\boxed{\text{Titian, not Tintoretto}.}
\]
Hence,
\[
\boxed{\text{Reason (R) is Incorrect}}
\]
Step 3: Choose the correct option.
Since Assertion (A) is true but Reason (R) is false,
\[
\boxed{\text{(C) (A) is correct but (R) is not correct.}}
\]