SN4 ""

No	Pattern	Freq
1	it have been [adj]	1262
2	it have been [adj]	954
3	it had been [adj]	487
4	it has been [adj]	447
5	it 's been [adj]	280
6	it have been [num]	141
7	it have been [det]	111
8	it have been possible	89
9	it have been possible	89
10	it have been one	50
11	it have been one	50
12	it have been difficult	48
13	it have been difficult	48
14	it have been [adj -er]	48
15	it have been necessary	45
16	it have been necessary	45
17	it have been good	44
18	it have been such	34
19	it have been such	34
20	it have been [adj]	33
21	it have been easy	30
22	it have been able	26
23	it have been able	26
24	it have been good	26
25	it have been impossible	24
26	it have been impossible	24
27	it have been easy	19
28	it have been hard	18
29	it have been clear	18
30	it have been hard	18