Ans. is 'c' i.e., 72 hours Platelets are provided as a pooled preparation from one or several donors, usually as a 6-unit bag, which is the usual amount given to an average-sized adult. Each unit contains approximately 8 x 101deg platelets and should increase the platelet count by about 7000-10,000/ pL in a 75kg adult. Platelets stored at room temperature can be used for up to 5 days and have a life span of 8 days. Those stored at 4degC are useful for only 24 hours (only 50-70% of total platelet activity is present at 6 hours) and have a life span of only 2-3 days. ABO compatibility should be observed for platelets, but is not essential. For each donor used, there is a similar risk of transmitting hepatitis and HIV as for one unit of blood. Platelet should be administered through a 170pm filter.