Suppose You Measure the Density (Mass Per Volume)of an Object

Multiple Choice

Suppose you measure the density (mass per volume) of an object moving by you at very high speed.How will its density compare to the density it would have at rest in your reference frame?

A) Its density would be lower.
B) Its density would be higher.
C) Its density would be the same.
D) There is no way to know,because relativity doesn't tell us anything about density.