14.4 In an unbiased p-n junction, holes diffuse from the p-region to n-region because:

(1) free electrons in the n-region attract them.
(2) they move across the junction by the potential difference.
(3) hole concentration in p-region is more as compared to n-region.
(4) all of the above.

Hint: A p-n junction is a boundary between two semiconductor material types.
Step 1: Identify the condition for the unbiased p-n junction.
The diffusion of charge carriers across a junction takes place from the region of higher concentration to the region of lower concentration. In this case, the p-region has a greater concentration of holes than the n-region. Hence, in an unbiased p-n junction, holes diffuse from the p-region to the n-region.