Step 1: Understanding the Concept
For a point \((x,y,z)\), the distance from the XY plane is \(|z|\) and the distance from the Y-axis is \(\sqrt{x^{2}+z^{2}}\).
Step 2: Distance a
For \((2,3,4)\), \(a=4\), so \(a^{2}=16\).
Step 3: Distance b
\(b=\sqrt{2^{2}+4^{2}}=\sqrt{20}\), so \(b^{2}=20\).
Step 4: Add
\(a^{2}+b^{2}=16+20=36\).
Final Answer:
The value of a squared plus b squared is 36.
\[ \boxed{\text{(D) }36} \]