Diffusion is a natural phenomenon which occurs when there is concentration difference between the two regions. The covalent bond is formed between the trivalent (or pentavalent) and semiconductor atom in p-type (or n-type). Thus there are many vacant places (holes) and electrons in the p-side and n-side respectively. Thus there are less or no electrons in p-side while there are many electrons in n-side. Clearly, there is concentration difference of electrons across the junction and diffusion will take place. This forces the covalent bond to be broken on the n-side so that the electrons freed from this bond, jumps to the vacant places in the p-side. Also when the electron jumps from the n-side to the p-side, a vacant place (hole) is created in n-side which represents that a hole has been moved from the p-side to the n-side.

Therefore, the correct answer is option C.