Exp) Option d is the correct answer.

The 52nd Constitutional Amendment Act, 1985 provided for the disqualification of the members of Parliament and the state legislatures on the ground of defection from one political party to another. The purpose of Anti defection law is to bring stability to governments by deterring MPs and MLAs from changing their political parties on whose ticket they were elected.

Option a is incorrect: Anti defection law applies equally to both the houses of Parliament (and State legislatures). Thus, nominated members irrespective of their membership of house are subject to provisions of Anti defection law. Hence nominated members of Rajya Sabha can be disqualified under defection charges if he/she joins political parties after six months of their nomination.

Option b is incorrect: Nominated member of the Parliament cannot be disqualified on the ground of his/her refusal to join any political party within six months of their nomination to the house. The tenth schedule (Anti defection law) provides nominated members a choice to join any political parties within six months of their nomination and by doing so they cannot attract defection charges.

Option c is incorrect: The tenth schedule (and Anti defection law) provides nominated members a choice to join any political parties within six months of their nomination and by doing so they cannot attract defection charges. So, the statement is incorrect.

Option d is correct: It is true that nominated members can be disqualified on the ground of defection, if he/she joins any political party after six months of their nomination.