Answer: D
The UNOPS Sustainable Investments in Infrastructure and Innovation (S3i) initiative focuses on (d) all four infrastructure sectors: affordable housing, mass rapid transport, healthcare, and renewable energy.
Explanation:
The UNOPS (United Nations Office for Project Services) Sustainable Investments in Infrastructure and Innovation (S3i) initiative aims to promote sustainable development through investments in various infrastructure sectors. According to the information available, the S3i initiative focuses on all four sectors mentioned in the question: affordable housing, mass rapid transport, healthcare, and renewable energy.
Authenticative Reference Source:
To obtain official and up-to-date information on the UNOPS S3i initiative and its focus areas, it is recommended to refer to the official website of UNOPS:
UNOPS Official Website: https://www.unops.org/