The locus of a point for which y = 0, z = 0 is

As x-axis lies on xy plane and xz.

So its distance from xy and xz plane is 0.

∴ By basic definition of 3-D coordinate we can say that y-coordinate and z–coordinate are 0.

∴ any point on X-axis has y and z coordinate = 0

∴ y = 0 and z = 0 can be considered as the equation of x-axis.

Hence, option(A) is the only correct choice.