| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | but have been unable | 20 |
|
| 2 | but [vb past] been unable | 11 |
|
| 3 | but had been unable | 11 |
|
| 4 | but have been unable | 6 |
|
| 5 | but [vb base] been unable | 6 |
|
