The correct answer is: B. specific volume
Specific volume is the volume of a unit mass of a substance. It is an intensive property, meaning that it does not depend on the size or shape of the object. Specific volume is often used in thermodynamics and fluid mechanics.
Specific weight is the weight of a unit volume of a substance. It is a derived quantity, meaning that it is calculated from other quantities, such as mass and density. Specific weight is often used in engineering and physics.
Specific speed is a dimensionless quantity that is used to compare the performance of different types of pumps. It is calculated by dividing the speed of a pump by the square root of the product of the density and the head of the pump. Specific speed is often used in hydraulic engineering.
Specific gravity is a dimensionless quantity that is used to compare the density of a substance to the density of water. It is calculated by dividing the density of the substance by the density of water. Specific gravity is often used in chemistry and physics.
In conclusion, specific volume is the only dimensionless quantity among the given options.