| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | they [vb mod] have been [v-ing] | 78 |
|
| 2 | they must have been [v-ing] | 18 |
|
| 3 | they should have been [v-ing] | 16 |
|
| 4 | they might have been [v-ing] | 15 |
|
| 5 | they would have been [v-ing] | 11 |
|
| 6 | they could have been [v-ing] | 8 |
|
| 7 | they may have been [v-ing] | 7 |
|
