SN4 ""

No	Pattern	Freq
1	[conj] it is [adv] difficult	203
2	[coord] it is [adv] difficult	82
3	that it is [adv] difficult	66
4	that it is [adv] difficult	66
5	[that] it is [adv] difficult	66
6	[subord] it is [adv] difficult	55
7	[noun] it is [adv] difficult	52
8	and it is [adv] difficult	47
9	and it is [adv] difficult	47
10	[noun sg] it is [adv] difficult	40
11	[adv] it is [adv] difficult	37
12	but it is [adv] difficult	35
13	but it is [adv] difficult	35
14	[adv] it is [adv] difficult	28
15	[verb] it is [adv] difficult	17
16	because it is [adv] difficult	16
17	because it is [adv] difficult	16
18	[pron] it is [adv] difficult	14
19	[noun pl] it is [adv] difficult	12
20	[Wh det] it is [adv] difficult	11
21	which it is [adv] difficult	11
22	which it is [adv] difficult	11
23	as it is [adv] difficult	9
24	as it is [adv] difficult	9
25	[Wh adv] it is [adv] difficult	9
26	[adj] it is [adv] difficult	8
27	practice it is [adv] difficult	8
28	practice it is [adv] difficult	8
29	although it is [adv] difficult	6
30	although it is [adv] difficult	6