Final answer:
Option B (-2 and 1) are like terms because they are both constants without any variable parts. Terms that have the same variables and powers or are both constants can be combined and are considered like terms.
Step-by-step explanation:
The question asks which of the following are like terms: A) 18x and 6z B) -2 and 1 C) 5y and 18x D) -15 and 1. Like terms are terms that have exactly the same variable parts, which means they have the same variables raised to the same powers. Numbers without variables are also considered like terms.
Looking at the options, B) -2 and 1 are like terms because they are both constants without any variable parts. Options A), C), and D) have variables that are different in each pair (x and z for A, y and x for C, and no variables at all for D, but D has two constants). Therefore, option B is the correct answer because both terms are constants and can be combined arithmetically.