Which of the following describes a quadratic expression?

A quadratic expression is defined by its degree, which is the highest power of the variable present in the expression. Specifically, a quadratic expression has a degree of two, meaning that the highest exponent on the variable (typically denoted as (x)) is two. This characteristic leads to the general form of a quadratic expression, which is (ax^2 + bx + c), where (a), (b), and (c) are constants and (a \neq 0).

Understanding the significance of the degree is crucial, as it determines the shape and properties of the graph of the expression, which is a parabola when plotted. The properties of the quadratic function, such as its vertex, direction of opening, and roots, are all derived from this degree.

The other choices refer to different types of expressions or functions:

• An expression with a degree of one defines a linear expression, which is a straight line when graphed.

• An expression with no variables is a constant, which does not fit the definition of a quadratic since it lacks a variable component altogether.

• An expression representing a linear function is also characterized by a degree of one and is thus not related to quadratics.

The correct answer directly aligns