SN4 ""

No	Pattern	Freq
1	[pron] must have been	1980
2	[pers pn] must have been	1552
3	[noun] must have been	928
4	it must have been	781
5	it must have been	781
6	[noun sg] must have been	546
7	he must have been	266
8	there must have been	264
9	[ex0] must have been	264
10	there must have been	264
11	he must have been	263
12	[noun pl] must have been	208
13	[noun prp] must have been	167
14	[adj] must have been	144
15	she must have been	139
16	she must have been	139
17	they must have been	132
18	they must have been	123
19	[Wh det] must have been	120
20	[det] must have been	119
21	i must have been	118
22	i must have been	117
23	you must have been	94
24	you must have been	93
25	[conj] must have been	89
26	that must have been	67
27	that must have been	67
28	which must have been	64
29	which must have been	64
30	[coord] must have been	58