Concept:
Woodcut is a relief printing process in which the raised surface receives ink while the carved-out portions remain blank.
In contrast, Etching is an intaglio printing process in which the incised lines or crevices hold the ink, while the raised surface is wiped clean and prints white. Thus, the printing principle of etching is opposite to that of woodcut.
Step 1: Examine Assertion (A).
Woodcut prints from raised surfaces, whereas etching prints from recessed lines.
Hence,
\[
\boxed{\text{Assertion (A) is Correct}}
\]
Step 2: Examine Reason (R).
In etching, ink remains only in the etched grooves or crevices, while the raised portions are wiped clean and therefore print blank.
\[
\boxed{\text{Reason (R) is Correct}}
\]
Step 3: Check whether (R) explains (A).
The Reason explains why etching is opposite to woodcut, since the two techniques use opposite printing surfaces.
Therefore,
\[
\boxed{\text{Both (A) and (R) are correct and (R) is the correct explanation of (A).}}
\]
Hence,
\[
\boxed{\text{(A)}}
\]