Firms use various methods for identifying customers such as​ ________ and​ ________.

A. observable characteristics such as​ age; their actions such as willingness to wait in long lines
B. observable characteristics such as willingness to wait in long​ lines; their actions such as whether or not they live a long time
C. the color of their​ hair; whether or not they roll their eyes at high prices
D. None of the above.