SN4 ""

No	Pattern	Freq
1	[pron] must have been an	31
2	[pers pn] must have been an	19
3	[noun] must have been an	12
4	it must have been an	11
5	it must have been an	11
6	there must have been an	10
7	[ex0] must have been an	10
8	there must have been an	10
9	[noun sg] must have been an	9
10	must have been [adv] an	6
11	must have been [adv] an	6
12	must have been an [adj]	26
13	must have been an [adj]	26
14	must have been an [noun]	22
15	must have been an [noun sg]	21
16	must have been an awful	5
17	must have been an awful	5