SN4 ""

No	Pattern	Freq
1	be [adv] [adv] difficult	493
2	[be] [adv] [adv] difficult	493
3	[is] [adv] [adv] difficult	311
4	is [adv] [adv] difficult	267
5	[verb] [adv] [adv] difficult	103
6	[adv] [adv] [adv] difficult	102
7	[art] [adv] [adv] difficult	79
8	[art] [adv] [adv] difficult	79
9	[adv] [adv] [adv] difficult	72
10	[am/are] [adv] [adv] difficult	71
11	are [adv] [adv] difficult	70
12	[pron] [adv] [adv] difficult	66
13	a [adv] [adv] difficult	61
14	[pers pn] [adv] [adv] difficult	60
15	it [adv] [adv] difficult	57
16	it [adv] [adv] difficult	57
17	be [adv] [adv] difficult	51
18	[be] [adv] [adv] difficult	51
19	a [adv] [adv] difficult	51
20	[was/were] [adv] [adv] difficult	49
21	[noun] [adv] [adv] difficult	48
22	's [adv] [adv] difficult	44
23	become [adv] [adv] difficult	40
24	[conj] [adv] [adv] difficult	40
25	was [adv] [adv] difficult	39
26	[coord] [adv] [adv] difficult	39
27	[noun sg] [adv] [adv] difficult	34
28	and [adv] [adv] difficult	30
29	and [adv] [adv] difficult	30
30	[vb pp] [adv] [adv] difficult	28