SN4 ""

No	Pattern	Freq
1	it have [adv] been [adj]	288
2	it has [adv] been [adj]	168
3	it have [adv] been [adj]	146
4	it have [not/n't] been [adj]	142
5	it have not been [adj]	142
6	it have not been [adj]	102
7	it had [adv] been [adj]	86
8	it have [adv] been possible	62
9	it have n't been [adj]	40
10	it have always been [adj]	38
11	it have always been [adj]	38
12	it have [adv] been easy	35
13	it 's [adv] been [adj]	32
14	it have never been [adj]	22
15	it have never been [adj]	22
16	it have [adv] been able	14
17	it have [adv] been necessary	14
18	it have also been [adj]	11
19	it have all been [adj]	11
20	it have [adv] been difficult	11
21	it have all been [adj]	11
22	it have also been [adj]	11
23	it have only been [adj]	9
24	it have only been [adj]	9
25	it have [adv] been clear	9
26	it have certainly been [adj]	6
27	it have [adv] been hard	6
28	it have certainly been [adj]	6
29	it have [adv] been popular	5