Short life span is of?
Leukocytes usually have a lifespan of a few months but a few might also live up to years.
Basophils have a lifespan of a few days.
Neutrophils in an inactivated state have a lifespan of 5-90 hours and activated neutrophils usually live for a few days.
Monocytes have a short lifespan and usually live for around 24 hours and undergo apoptosis soon after.
So, the correct answer is 'Monocytes'.