In an unbiased p-n junction, holes diffuse from the p-region

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

1. the potential difference across the p-n junction
2. the attraction of free electrons of n-region
3. the higher hole concentration in p-region than that in n-region
4. the higher concentration of electrons in the n-region than that in the p-region

In p-region of p-n junction holes concentration > electrons concentration and in n-region electrons concentration > holes concentration.