Final answer:
The correct answer is option B. In the expression 3a² + 3a - 12, the 3a is a factor, which is a quantity by which a term is multiplied within an algebraic expression.
Step-by-step explanation:
3a in the expression 3a² + 3a - 12 is described as a factor. In algebra, a factor is a quantity by which a term is multiplied in an algebraic expression or an equation. Each term in an expression is made up of factors that are multiplied together. For example, in the term 3a², the number 3 and the variable 'a' squared (a²) are factors.
The term 3a appears as both a factor in the term 3a² and as a separate term 3a in the expression. It is not the sum, as a sum refers to the result of adding terms together. It is also not a quotient, which is the result of division between two terms.