| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun] must have been [v-ing] [prep] | 19 |
|
| 2 | [noun] must have be [v-ing] [prep] | 19 |
|
| 3 | [noun] must have be [v-ing] [prep] | 19 |
|
| 4 | [noun sg] must have be [v-ing] [prep] | 8 |
|
| 5 | [noun prp] must have be [v-ing] [prep] | 7 |
|
| 6 | [noun] must have be [v-ing] in | 6 |
|
