Final answer:
The correct expression for the electric field intensity at the surface of the plate due to a point charge is E = kQ/r².
Step-by-step explanation:
The expression for the electric field intensity at the surface of the plate due to a positive point charge is given by the equation E = kQ/r², where E represents the electric field intensity, k is the Coulomb's constant, Q is the magnitude of the charge, and r is the distance from the charge to the point where the electric field is being calculated. Since the question specifically asks about the electric field at the surface of a charged plate near a positive point charge, and no information is given about variation of the field with distance or any non-spherical charge distribution, the general expression for the electric field due to a point charge is applicable here. In a situation where the charged plate is flat and infinite, the electric field is uniform and would not follow an inverse square law as a point charge would, therefore the option (b) E = kQ/r, (c) E = kQ/r³, and (d) E = kQ would not apply.