| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must be [v-ing] [prep] the [noun sg] | 17 |
|
| 2 | must be [v-ing] [prep] a [noun sg] | 8 |
|
| 3 | must be [v-ing] to [art] [noun sg] | 5 |
|
| 4 | must be [v-ing] in [art] [noun sg] | 5 |
|
