In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

[Q]: Lin and Shu proposed the density-wave theory to explain how the structure of these entities is sustained. The most accurate method for measuring the distances to distant ones uses a relation between their maximum rotational velocity and absolute magnitude, which is known as the Tully-Fisher method. They are generally blue because of their high content of old stars, and one type of them features arms that emanate from each end of a namesake structure. They have discs like the lenticular type, but contain much more angular momentum than the elliptical type. FTP name these galaxies, some of which are barred, including the Milky Way.
[A]: Science


[Q]: It holds only when the molecular attraction between different components is equal to the attraction of any one component in its pure state. Dealing primarily with changes in colligative properties, it allows for the calculation of molecular weights of dissolved substances and leads to the definition of a solution as ideal. FTP, identify this law that relates the vapor pressure and mole fraction of a solution, a law named for its French discoverer.
[A]: Science


[Q]: The Kepler conjecture states that this quantity is maximized for HCP and FCC crystals. The reciprocal of this quantity is called specific volume. This quantity is the ratio between kinematic and dynamic viscosity. The melting point line has a negative slope when this quantity is greater for liquids than for solids. The ratio of it to a reference standard is specific gravity. Among elements, this quantity is greatest for osmium and iridium. For water, it's maximized at 4 degrees Celsius. If two substances are immiscible, the one with a greater value for this will form the bottom layer. For 10 points, name this quantity equal to mass over volume.
[A]:
Science