The correct answer is: All of the above.
Early marriage is a common practice in many parts of Assam, and it can contribute to a higher fertility rate. This is because girls who marry early are more likely to have children at a young age, and they are also more likely to have more children overall.
Limited access to contraception is another factor that can contribute to a higher fertility rate. In some parts of Assam, it is difficult to obtain contraception, and this can make it difficult for women to control their fertility.
Preference for sons is another factor that can contribute to a higher fertility rate. In some cultures, there is a preference for sons, and this can lead to families having more children in order to have a son.
All of these factors can contribute to a higher fertility rate in certain communities of Assam.