In an unbiased p-n junction, holes diffuse from the p-region to the n-region because.
Hole concentration in p-region is more as compared to n-region.
Explanation of correct option:-
Option (C):- Hole concentration in p-region is more as compared to n-region.
Explanation of incorrect option:-
Option (A):- Free electrons in the n-region attract them.
Option (B):- They move across the junction by the potential difference
Option (D):- All of the above
Therefore, In an unbiased p-n junction, holes diffuse from the p-region to the n-region because hole concentration in p-region is more as compared to n-region
Hence, option (C) is correct.