The correct answer is option 3, the 73rd Amendment of the Constitution of India. This amendment deals with the issue of strengthening the Panchayati Raj.

Option 1, the 42nd Amendment, and option 2, the 44th Amendment, do not specifically deal with the Panchayati Raj. The 42nd Amendment made several changes to the Constitution, including the infamous insertion of the words "socialist" and "secular" in the Preamble. The 44th Amendment, on the other hand, focused on safeguarding certain fundamental rights.

Option 4, the 86th Amendment, also does not deal with the Panchayati Raj. This amendment lowered the voting age from 21 to 18 years.

It is important to note that the Panchayati Raj system in India was established through the 73rd Amendment Act of 1992. This amendment added Part IX to the Constitution, which provides for a three-tier system of Panchayati Raj institutions at the village, intermediate, and district levels.

Therefore, the correct answer is option 3, the 73rd Amendment, which specifically deals with the strengthening of the Panchayati Raj system in India.