| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [modal v] be [v-ing] [adv] | 2479 |
|
| 2 | must be [verb] [adv] | 1401 |
|
| 3 | must be [v-ing] [adv] | 172 |
|
| 4 | must [be] [v-ing] [adv] | 172 |
|
| 5 | must [be] [v-ing] [adv] | 172 |
|
