Multiple choice The life span of blood platelets in mammals is about 3 days 5 days 10 days 20 days Reveal answer Fill a bubble to check yourself B Correct answer Explanation Blood platelets (thrombocytes) have a lifespan of approximately 5-7 days in mammals. Option B at 5 days is the closest. Platelets are much shorter-lived than RBCs (120 days) and don't last 10-20 days.