The Lohit and Subansiri rivers both flow through Arunachal Pradesh and are significant tributaries of the Brahmaputra River. The Lohit originates in Tibet and enters Arunachal Pradesh, while the Subansiri flows through the eastern part of the state, contributing to the rich hydrological network. In contrast, the Barak River primarily flows through the state of Manipur and does not originate in or traverse Arunachal Pradesh, making the correct option 2 and 3 only. This distinction is important in the context of understanding the river systems in Northeast India, which are frequently discussed in UPSC Prelims as part of geographic and environmental studies.