Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Discipline | Championship | Circuit | Event | Session |
| --- | --- | --- | --- | --- |
| Stock car | Sprint Cup Series | Daytona International Speedway | UNO Twin 125 Qualifiers | Qualifying |
| Stock car | Whelen Modified Tour | Martinsville Speedway | Winn-Dixie 500 | Race |
| Drag Racing | NHRA Winston Drag Racing Series | Indianapolis Raceway Park | Mac Tools US Nationals | Qualifying |
| Stock car | ARCA Series | Daytona International Speedway | Daytona ARCA 200 | Race |
| Open Wheel | USAC National Championship | Williams Grove Speedway | Indianapolis Sweepstakes | Race |
Question:
For the USAC National Championship, what is the Discipline?
Answer:
Open Wheel