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:
| COMPANY NAME | Holding Companies | Subsidiaries | Description of activities | Parent (holding) company |
| --- | --- | --- | --- | --- |
| APOLLO DOMINION INVESTMENTS LIMITED | 5.0 | 0.0 | Investment holding company. | BESCOT ENTERPRISES LIMITED |
| CLEAR CHANNEL ENTERTAINMENT FACILITATION LIMITED | 5.0 | 0.0 | Financial intermediation | CLEAR CHANNEL ENTERTAINMENT (MUSIC) UK LIMITED |
| LOUIS BARNETT & SON LIMITED | 5.0 | 0.0 | Dormant. | CLEAR CHANNEL UK LIMITED |
| POSTERMOBILE LIMITED | 5.0 | 4.0 | Selling of advertising space | CLEAR CHANNEL UK LIMITED |
| BARRETT PETRIE SUTCLIFFE LIMITED | 5.0 | 0.0 | Advertising | CLEAR CHANNEL UK LIMITED |
| ROCKBOX LIMITED | 5.0 | 0.0 | Product advertising. | CLEAR CHANNEL UK LIMITED |
| TRACEMOTION LIMITED | 5.0 | 1.0 | The provision of managemenet services | CLEAR CHANNEL UK LIMITED |
| CLEAR CHANNEL (CENTRAL) LIMITED | 5.0 | 12.0 | Score outdoor group | CLEAR CHANNEL UK LIMITED |
| F M MEDIA LIMITED | 5.0 | 0.0 | Advertising | CLEAR CHANNEL UK LIMITED |
| TAXI MEDIA HOLDINGS LIMITED | 5.0 | 1.0 | Dormant. | D CLEAR CHANNEL UK LIMITED |
| CLEAR CHANNEL (NORTH WEST) LIMITED | 6.0 | 2.0 | Engaged as outdoor advertising contractors. | CLEAR CHANNEL (CENTRAL) LIMITED |
| CLEAR CHANNEL (SOUTH WEST) LIMITED | 6.0 | 0.0 | Dormant. | CLEAR CHANNEL (CENTRAL) LIMITED |
| GROSVENOR ADVERTISING LIMITED | 6.0 | 0.0 | Dormant. | CLEAR CHANNEL (CENTRAL) LIMITED |
| POSTERMOBILE ADVERTISING LIMITED | 6.0 | 0.0 | Dormant. | POSTERMOBILE LIMITED |
| KMS ADVERTISING LIMITED | 6.0 | 0.0 | Dormant. | POSTERMOBILE LIMITED |
| TAXI MEDIA LIMITED | 6.0 | 0.0 | Taxi advertising contractors | TAXI MEDIA HOLDINGS LIMITED |
Question:
What is the largest number of holding companies?
Answer:
6.0