Chapter 1, Equations and Inequalities - 1.2 Evaluate and Simplify Algebraic Expressions - 1.2 Exercises - Skill Practice - Page 14: 33

D

Like terms must (1) be raised to the same power and (2) consist of the same variable (i.e. x and y are not like terms). It is also important to note that numbers are all like terms with each other when not multiplied by anything. Thus, we see that answer D represents the only set of like terms.