Step 1: Find Normal Vector
The line joining the origin (0,0,0) and the foot $P(2, -1, 4)$ is the normal to the plane.
Normal DRs: $(2-0, -1-0, 4-0) = (2, -1, 4)$.
Step 2: General Plane Equation
$a(x-x_1) + b(y-y_1) + c(z-z_1) = 0$.
$2(x-2) - 1(y+1) + 4(z-4) = 0$.
Step 3: Simplification
$2x - 4 - y - 1 + 4z - 16 = 0$.
$2x - y + 4z - 21 = 0$.
Step 4: Conclusion
The equation is $2x - y + 4z - 21 = 0$.
Final Answer:(D)