The right option is; orbital period
T stands for orbital period.
Orbital period is the time a certain astronomical object such as planets takes to complete one orbit (360° revolution) around another object such as sun or stars. Orbital period is expressed in different units of time, usually in years, days or hours.
Cytoplasmic uses actin and myosin for the movement of the cytosol which causes the organelles to move inside the cell.
Biology is the study of living organisms, divided into many specialized fields that cover their morphology, physiology, anatomy, behavior, origin, and distribution.
This is basically the definition of biology, so you may need to add a little more detail. This is a great way to get it started though!!!
Hope this helps!!
