Option (C) is correct. According to the textbook context, in a p-type semiconductor, the concentration of holes is more than the concentration of electrons. During the formation of p-n junction, due to the concentration gradient across p- and n- sides, holes diffuse from p-side to n-side (p → n). This motion of charge carriers gives rise to diffusion current across the junction. Option (A) is incorrect as diffusion is not due to attraction by free electrons. Option (B) is incorrect because the potential difference (barrier potential) actually opposes the movement of carriers, as stated: 'The polarity of this potential is such as to oppose further flow of carriers.' Therefore, holes diffuse from p-region to n-region solely due to concentration gradient, making (C) the correct answer.