Which human body organ can regrow ?

The correct answer is Option (1) → Liver

The liver is the one internal organ of the human body that can regrow (regenerate) its lost tissue. When part of it is removed or damaged, the remaining liver cells divide and the organ grows back to about its full size in a few weeks.

This is why a living person can donate part of the liver for a transplant: both the donor’s and the receiver’s pieces grow into working livers.