The sedimentation coefficient:

is expressed in Svedberg units, named after the scientist who invented the ultracentrifuge.
is affected by the shape of the sedimenting particle.
is directly proportional to the molecular weight of a particle in an ultracentrifuge.
is obtained when a particle has neutral buoyant density.
values are additive, so a 50S ribosome will dissociate to two 25S subunits.

option D is incorrect

Explanation:

the sedimentation coefficient is measured in Svedberg units named after the scientist Theodore Svedberg. the shape of the particle being measured in the ultracentrifuge is one of the factors that determines the sedimentation coefficient. the values are usually not additive as the sedimentation coefficient is based on the rate at which a particle sediments in an ultracentrifuge and not on the size. for example, the sedimentation coefficient of eukaryotic ribosome is 80S but is made up of the 60S large subunit and the 40S small subunit.