Final answer:
An algebraic expression is a mathematical phrase containing variables, numbers, and operations, but not necessarily an equals sign. An equals sign would turn the expression into an equation, which is a different mathematical concept. Hence, 'c) Equals sign' is not a necessary part of an algebraic expression.
Step-by-step explanation:
An algebraic expression is a mathematical phrase that includes variables, numbers, and operations but does not necessarily include an equals sign. Unlike an equation, an algebraic expression represents a value that can take on different outcomes depending on the input values of the variables. It functions similarly to a sentence in a language, where the structure gives meaning, and the specific symbols used (like x, n, t) are arbitrary as long as they are used consistently throughout the expression.
To clarify with an example, consider the expression 2x + 3. It includes a variable (x), a number (2, 3), and an operation (addition). You can perform operations like multiplication or division on each term of the expression, but an expression itself does not assert an equality; that is the role of an equation. Just like in language, the symbols we choose (like x or n) are just labels with no intrinsic meaning; they represent quantities that can change or vary, hence the term variable.
In conclusion, the part of an algebraic expression that is not necessary is the equals sign. An equals sign turns an expression into an equation, which is a statement that two expressions are equal in value. Therefore, the correct answer to your question is 'c) Equals sign'.