Concept:
In the Elements of Art, a line is defined as the path created by a moving point. When an artist moves the tip of a pencil, pen, brush, stylus, or any other drawing instrument across a surface, the moving point produces a line.
The character of the line depends on how the instrument is moved. A line may be thick or thin, straight or curved, broken or continuous, light or dark, smooth or rough. Thus, the movement of the point directly determines the quality of the line.
Step 1: Examine Assertion (A).
A moving point, represented by the tip of a drawing instrument, creates a line on a surface.
\[
\boxed{\text{Assertion (A) is Correct}}
\]
Step 2: Examine Reason (R).
The quality of a line depends on how the artist moves the drawing instrument, producing different visual effects.
\[
\boxed{\text{Reason (R) is Correct}}
\]
Step 3: Check whether (R) explains (A).
Since a moving point creates a line, and the manner in which that point moves determines the line's qualities, the Reason correctly explains the Assertion.
Therefore,
\[
\boxed{\text{Both (A) and (R) are correct and (R) is the correct explanation of (A).}}
\]
Hence,
\[
\boxed{\text{(A)}}
\]