Which quantity has both magnitude and direction?

The quantity that has both magnitude and direction is a vector quantity. Vectors are fundamental in various fields, including physics and engineering, because they provide not only the size or amount of a quantity but also its orientation in space. For example, if you're considering velocity, it involves how fast an object is moving (magnitude) and the direction in which it's moving. This dual characteristic of vectors is crucial for accurately describing physical phenomena, making them distinct from scalar quantities, which only have magnitude and no direction.

In contrast, scalar quantities, like temperature or mass, are defined solely by their magnitude. Specific gravity is a dimensionless quantity that compares the density of a substance to the density of a reference substance, typically water, without providing directional information. A bathymetric map represents underwater depth or topography but does not convey either magnitude or direction of a quantity; it merely illustrates variations in depth.

Therefore, the definition and characteristics of vector quantities illustrate their importance in contexts where direction affects the behavior of a system, helping to clarify why this option is the right choice.