This answer is correct because it matches the requirement of the Materials and Resources Credit, Purchasing - Lamps, which aims to reduce the environmental and health impacts of mercury used in lamps.The credit requires projects to purchase lamps that have a mercury content of 80 picograms per lumen hour or less for at least 90% of the total number of lamps purchased during the performance period1. The other options are incorrect because they either have a higher mercury content threshold or a higher percentage of lamps to meet the threshold.
References: =LEED v4.1 OPERATIONS AND MAINTENANCE - WAP Sustainability Consulting, page
40;LEED v4: Building Operations + Maintenance Guide | U.S. Green Building Council, page 40.