The correct answer is option 2, Chandigarh.

The child-sex ratio refers to the number of females per 1000 males in the age group of 0-6 years. A lower child-sex ratio indicates a higher level of gender discrimination and potentially harmful practices towards female children.

Option 1, Dadra and Nagar Haveli, is not the correct answer as it is a Union Territory, but it does not have the lowest child-sex ratio.

Option 3, Andaman and Nicobar Islands, is not the correct answer as it is also a Union Territory, but it does not have the lowest child-sex ratio.

Option 4, Daman and Diu, is not the correct answer as it is a Union Territory, but it does not have the lowest child-sex ratio.

Therefore, the correct answer is option 2, Chandigarh, as it has the lowest child-sex ratio among the Union Territories.