| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | had be [v-ing] for several | 10 |
|
| 2 | had [been] [v-ing] for several | 10 |
|
| 3 | had been [v-ing] for several | 10 |
|
| 4 | had [be] [v-ing] for several | 10 |
|
