| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | had been operate | 33 |
|
| 2 | had [been] operate | 33 |
|
| 3 | had be operate | 33 |
|
| 4 | had [be] operating | 19 |
|
| 5 | had [be] operated | 14 |
|
