The National Dope Testing Laboratory is an important institution in India that is responsible for conducting tests to detect the use of prohibited substances in sports. It ensures fair play and integrity in sports by detecting athletes who may be using performance-enhancing drugs.

According to the correct answer provided in the question, the National Dope Testing Laboratory functions under the Ministry of Youth Affairs and Sports. This means that it operates under the jurisdiction and supervision of this ministry.

Option 1, "Ministry of Health and Family Welfare," is incorrect. Although the health and well-being of athletes is important, the National Dope Testing Laboratory does not fall under the purview of this ministry.

Option 2, "Ministry of Science and Technology," is also incorrect. While scientific knowledge and techniques are used in conducting drug tests, the National Dope Testing Laboratory is not directly associated with this ministry.

Option 4, "Ministry of Home Affairs," is also incorrect. The National Dope Testing Laboratory`s role is not related to security or law enforcement, which falls under the responsibility of the Ministry of Home Affairs.

Therefore, the correct answer is option 3, "Ministry of Youth Affairs and Sports."