- Strengthening troop presence (3) is a standard and necessary military response to deter further incursions and protect territorial integrity. - India and China have established frameworks, such as the Special Representatives (SR) talks and various border mechanisms (Working Mechanism for Consultation and Coordination on India-China Border Affairs - WMCC), to discuss and resolve border issues peacefully (2). - Lodging a diplomatic protest (1) is also a very likely initial step, often accompanying or preceding other actions. - Lodging a complaint against China at the UN (4) is highly unlikely for a bilateral border dispute between two large nations with established bilateral mechanisms; it would be seen as an escalation and is impractical given China's veto power in the Security Council.