Option (1) is the correct answer as the body is able to differentiate between ‘self’ and ‘non-self’ and the cell-mediated immune response is responsible for the graft rejection.

Option (2) is incorrect as body of higher vertebrates have the ability to differentiate foreign organisms from self cells.

Option (4) is incorrect as the autoimmune response occur when the body’s immune system fails to recognize ‘self’ from ‘non-self’ and starts destroying the body’s own cells.