###### Answer: C.

In mathematics the graph of a function f is the set of ordered pairs ( x y) where f ( x ) = y.In the common case where x and f ( x ) are real numbers these pairs are Cartesian coordinates of points in two-dimensional space and thus form a subset of this plane.. In the case of functions of two variables that is functions whose domain consists of pairs ( x y) the graph usually refers to the set …

In graph theory Hedetniemi’s conjecture formulated by Stephen T. Hedetniemi in 1966 concerns the connection between graph coloring and the tensor product of graphs .This conjecture states that (×) = {() ()}.Here () denotes the chromatic number of an undirected finite graph .. The inequality χ( G × H) ≤ min {χ( G ) χ(H)} is easy: if G is k-colored one can k-color G × H by using the …

More formally f = g if f ( x ) = g ( x ) for all x ∈ X where f : X → Y and g : X → Y. [8] [9] [note 4] The domain and codomain are not always explicitly given when a function is defined and without some (possibly difficu…