The correct answer is indeed 1, 2, 3, and 4, as all these expenditures fall under the category of Non-Plan Expenditure in the context of the Union Budget. Non-Plan Expenditure refers to government spending that is not directly associated with developmental or planned activities, including mandatory and recurring payments such as defence expenditure, interest payments on government debt, salaries, pensions, and subsidies. This category reflects the commitment of the government to meet fixed obligations and maintain essential services, which is crucial for understanding fiscal policy, budget allocation, and economic management as required in UPSC Prelims GS Paper I.