The correct answer is (a) Parsi.
Parsi people have the lowest fertility rate in India, with an average of 1.5 children per woman. This is significantly lower than the national average of 2.2 children per woman. There are a number of reasons for this, including the fact that Parsi families are typically small, and that many Parsi women choose to have careers rather than children.
Sikhs have a fertility rate of 2.1 children per woman, which is close to the national average. This is likely due to the fact that Sikhism is a religion that values family life. Jains have a fertility rate of 2.0 children per woman, which is also close to the national average. This is likely due to the fact that Jainism is a religion that values non-violence and compassion, which may lead to people choosing to have smaller families. Marwaris have a fertility rate of 2.5 children per woman, which is higher than the national average. This is likely due to the fact that Marwaris are a community that values tradition and family, and that many Marwari women choose to stay at home and raise children.
It is important to note that these are just averages, and there is a great deal of variation within each community. There are many Parsi families with more than two children, and many Sikh, Jain, and Marwari families with fewer than two children.