Which of the Following Variables Would Be Appropriate to Graph

Which of the following variables would be appropriate to graph using a pie or bar graph?
$\begin{array}{llll}\text { a. Annual income for } 20 \text { employees } & \text { Yes } & \text { or } & \text { No } \\ \text { b. The favorite baseball team of } 30 \text { students } & \text { Yes } & \text { or } & \text { No } \\ \text { c. The number of pages in } 15 \text { textbooks } & \text { Yes } & \text { or } & \text { No } \\ \text { d. The country of origin of } 25 \text { immigrants } & \text { Yes } & \text { or } & \text { No }\end{array}$