SN4 ""

No	Pattern	Freq
1	it have been [vb pp] [prep] [det]	135
2	it has been [vb pp] [prep] [det]	91
3	it have been [vb pp] [prep] some	43
4	it have been [vb pp] by [det]	32
5	it had been [vb pp] [prep] [det]	30
6	it have been [vb pp] for [det]	29
7	it have been [vb pp] in [det]	20
8	it have been [vb pp] [prep] many	20
9	it have been known [prep] [det]	14
10	it have been [vb pp] [prep] that	13
11	it have been [vb pp] [prep] this	12
12	it have been [vb pp] at [det]	11
13	it have been [vb pp] [prep] several	10
14	it 's been [vb pp] [prep] [det]	10
15	it have been used [prep] [det]	10
16	it have been [vb pp] [prep] all	10
17	it have been [vb pp] on [det]	8
18	it have been suggested [prep] [det]	8
19	it have been [vb pp] from [det]	7
20	it have been [vb pp] to [det]	6
21	it have been [vb pp] [prep] both	6
22	it have been shown [prep] [det]	5
23	it have been [vb pp] [prep] any	5
24	it have been [vb pp] above [det]	5
25	it have been argued [prep] [det]	5