On a survey of how students spend their time, one question asks, "Which of the following best describes your employment status?" The response options provided are

a. not employed
b. employed part-time
c. employed full-time
d. full-time student
e. other.

In the example, which of the following characteristics of coding rules did the researcher fail to address adequately?

1. Mutual exclusivity
2. Appropriate categories
3. Single dimension
4. Exhaustive options