| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have [been] [verb] for | 36 |
|
| 2 | must have been [verb] for | 36 |
|
| 3 | must have [been] [v-ing] for | 18 |
|
| 4 | must have [been] [vb pp] for | 18 |
|
| 5 | must have [been] looking for | 5 |
|
| 6 | must have [been] look for | 5 |
|
