The UNOPS Sustainable Investments in Infrastructure and Innovation (S3i) initiative primarily targets sectors that promote sustainable development objectives. Among the mentioned sectors, affordable housing, mass rapid transport, and renewable energy align closely with the UN's Sustainable Development Goals (SDGs), particularly in addressing climate action, sustainable cities, and equitable infrastructure. While healthcare is a critical sector, the S3i initiative specifically focuses on investments that tackle infrastructural sustainability and innovation, thus emphasizing only three of the four listed sectors. This distinction highlights the initiative's strategic role in fostering development that is environmentally friendly and socially responsible, which is a key theme in UPSC Prelims GS Paper I related to sustainability and development policies.