This is some data of before and after students take a class:
| Question1 Before | Question 1 After |
| A | A |
| B | C |
| C | C |
| C | C |
| D | C |
| C | C |
| C | C |
| C | C |
| A | A |
| B | C |
Before, students selcted A, B, and C as answers. After most of them realized C was the correct answer. Some still selected A, but none selected B. However, in my final graph, I only can chart A and C. How would I include that B is 0?