| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [verb] been about [adj] years | 6 |
|
| 2 | must [verb] been about [num] years | 6 |
|
| 3 | must [vb infin] been about [adj] years | 6 |
|
| 4 | must have been about [adj] years | 6 |
|
| 5 | must have been about [adj] years | 6 |
|
