To create a two-way table to analyze the students' preferences for painting (water color or oil painting) across different classes, the art teacher should choose variables that will allow for a clear comparison between the different classes and their respective painting preferences.
The best option for the row and column headings would be:
Class number (rows) and painting preference (columns)
With this setup, each class would be a row, and the columns would represent the preferences for water color and oil painting. This structure allows the teacher to easily see the distribution of preferences among the different classes.
So, the correct option from your list is:
class number and painting preference.