Which of the following is a member of the set of whole numbers and their opposites?

Whole numbers are defined as the set of non-negative integers that include zero and the positive integers (0, 1, 2, 3, ...). The phrase "their opposites" refers to the negative counterparts of these whole numbers, creating the set that includes both whole numbers and their negatives (which are integers).

An integer is characterized as any whole number, whether it's positive, negative, or zero. Therefore, integers encompass the entire range of whole numbers along with their opposites. This makes integers the perfect representation of the set being asked about, as they indeed include both the whole numbers and their negative versions.

The other options, such as fractions, decimals, and rational numbers, do not specifically describe the set that combines whole numbers and their opposites. Fractions can represent parts of whole numbers and are not considered whole numbers themselves, decimals can express values between integers, and rational numbers include fractions and decimals but also extend to integers. Thus, while they relate to numbers in general, they do not specifically fulfill the criteria of being whole numbers plus their opposites as integers do.