**Explanation:**

When two shafts of the same length transmit equal torque and have equal maximum stress, the following conditions can be assumed:

1. **Equal Torque:** The torque transmitted by both shafts is the same. This implies that the torque equation for solid and hollow shafts can be equated:

T = (π/16) * (d^3 - di^3) * τ_max
where,
T = torque
d = outer diameter of the solid shaft
di = inner diameter of the hollow shaft
τ_max = maximum stress in the shaft

2. **Equal Maximum Stress:** The maximum stress in both shafts is equal. This implies that the maximum shear stress equation for solid and hollow shafts can be equated:

τ_max = (16 * T) / (π * (d^3 - di^3))
where,
T = torque
d = outer diameter of the solid shaft
di = inner diameter of the hollow shaft
τ_max = maximum stress in the shaft

Now, we can analyze the given options:

a) **Polar Moment of Inertia:** The polar moment of inertia (J) is related to the shaft's resistance to torsion. It depends on the geometry and distribution of material around the axis of rotation. For a solid shaft, J = (π/32) * d^4, and for a hollow shaft, J = (π/32) * (d^4 - di^4). Since the torque and maximum stress are equal for both shafts, the polar moments of inertia will be different.

b) **Polar Modulus of Section:** The polar modulus of section (Wp) is related to the resistance of a shaft to angular distortion. It is given by the formula Wp = J/r, where J is the polar moment of inertia and r is the distance from the center of the shaft to the outermost fiber. As the polar moment of inertia is different for the solid and hollow shaft, the polar modulus of section will also be different.

c) **Angle of Twist:** The angle of twist (φ) is related to the amount of torsion or rotation experienced by a shaft under a given torque. It depends on the material properties, geometry, and length of the shaft. In this case, the torque and maximum stress are equal for both shafts, but the geometry (polar moment of inertia) is different. Hence, the angle of twist will also be different.

d) **None of the Above:** Since options a), b), and c) are incorrect, the correct answer is d) None of the above.

Therefore, the correct answer is option **B) Polar modulus of section**.