The line containing the points \((-2, 3)\) and \((2, 3)\) is a horizontal line, positioned at \(y = 3\).
When this line is reflected across the x-axis, the y-coordinates of every point on the line change sign. Therefore, the new points after reflection will be \((-2, -3)\) and \((2, -3)\).
To determine the length of the reflected line, we can find the distance between the two reflected points:
\[ \text{Distance} = |x_2 - x_1| = |2 - (-2)| = |2 + 2| = |4| = 4 \text{ units} \]
Thus, the length of the reflected line is \(4\) units.
The correct answer is:
4 units.