46.
The answer is: B
Explanation
The correct option is B: 52nd Constitutional Amendment.
The Anti-defection law was added to the Constitution of India by the 52nd Amendment Act of 1985, which inserted the Tenth Schedule in the Constitution.
The law was enacted to prevent legislators from changing parties for personal or political motives, and to ensure the stability of the government. The law lays down the grounds and process for disqualification of MPs and MLAs on the basis of defection.
The law also allows for the merger of parties if at least two-thirds of the members of a party agree to the merger. The law was further strengthened by the 91st Amendment Act of 2003, which added some more provisions to prevent defection.