Public investment in agriculture refers to government expenditures aimed at improving the agricultural sector, including infrastructure development, technological improvements, and providing institutional support. Statement 1 is incorrect: Fixing the Minimum Support Price (MSP) is a policy decision, not an investment. While it affects the agricultural sector, it is not a direct public investment in terms of capital expenditure. Statement 2 is correct: The computerization of Primary Agricultural Credit Societies (PACS) is a public investment because it involves government funds directed towards modernizing agricultural credit systems, enhancing efficiency, and accessibility for farmers. Statement 3 is correct: Social Capital development is a public investment in agriculture, as it involves building networks and community-based resources that help farmers improve productivity and access to resources. Statement 4 is incorrect: Free electricity supply is more of a subsidy, not a direct public investment in the form of capital expenditure. Statement 5 is incorrect: Waiver of agricultural loans is a policy measure aimed at alleviating farmer debt but does not qualify as an investment in infrastructure or capital. Statement 6 is correct: The setting up of cold storage facilities by the government is a direct public investment aimed at improving agricultural infrastructure and reducing post-harvest losses. Hence, option C is the correct answer.