SN4 ""

No	Pattern	Freq
1	[noun] but [pers pn] could have been	6
2	but [pers pn] could [adv] have been	25
3	but [pers pn] could [adv] have been	16
4	but [pers pn] could [not/n't] have been	9
5	but [pers pn] could not have been	9
6	but [pers pn] could n't have been	8
7	but [pers pn] could easily have been	6
8	but [pers pn] could easily have been	6
9	but [pers pn] could have been [verb]	13
10	but [pers pn] could have been [adj]	13
11	but [pers pn] could have been [vb pp]	9
12	but [pers pn] could have been [art]	9
13	but [pers pn] could have been [art]	9
14	but [pers pn] could have been [prep]	7
15	but [pers pn] could have been a	7
16	but [pers pn] could have been [adv]	7
17	but [pers pn] could have been [prep]	7
18	but [pers pn] could have been [adv]	7
19	but [pers pn] could have been a	6
20	but [pers pn] could have been [det]	5