Given:

• The fly is 1 meter from one wall (yz-plane), so its x-coordinate is 1.
• The fly is 8 meters from the other wall (xz-plane), so its y-coordinate is 8.
• The fly is 9 meters from point P (the origin).

To find the fly's distance from the ceiling (xy-plane), we use the distance formula.

Step 1: Apply the distance formula: Distance = $\sqrt{[(x - 0)^2 + (y - 0)^2 + (z - 0)^2]}$ $9 = \sqrt{[(1)^2 + (8)^2 + z^2]}$ $9 = \sqrt{[1 + 64 + z^2]}$ $9 = \sqrt{[65 + z^2]}$

Step 2: Solve for z: Square both sides to eliminate the square root: $81 = 65 + z^2$ $z^2 = 81 - 65$ $z^2 = 16$ $z = 4$

Conclusion: The fly is 4 meters away from the ceiling. Answer: A. 4