The distance of a point \( P(a, b, c) \) from the y-axis is the perpendicular distance from \( P \) to the y-axis.
The y-axis corresponds to the line where \( x = 0 \) and \( z = 0 \).
The perpendicular distance is: \[ \text{Distance} = \sqrt{(a - 0)^2 + (c - 0)^2} = \sqrt{a^2 + c^2}. \]
Therefore, the correct answer is (C) \( \sqrt{a^2 + c^2} \).
The correct IUPAC name of \([ \text{Pt}(\text{NH}_3)_2\text{Cl}_2 ]^{2+} \) is: