SN4 ""

No	Pattern	Freq
1	it is [adj] [prep] this	127
2	it is [adj] [prep] this	123
3	it is [adv] [prep] this	51
4	it is [adv] [prep] this	42
5	it is [verb] [prep] this	39
6	it is [vb pp] [prep] this	33
7	it is clear [prep] this	18
8	it is only [prep] this	18
9	it is clear [prep] this	18
10	it is only [prep] this	18
11	it is [subord] [prep] this	15
12	it is because [prep] this	15
13	it is [noun] [prep] this	15
14	it is [conj] [prep] this	15
15	it is because [prep] this	15
16	it is important [prep] this	12
17	it is important [prep] this	12
18	it is appropriate [prep] this	10
19	it is appropriate [prep] this	10
20	it is [noun pl] [prep] this	8
21	it is evident [prep] this	6
22	it is evident [prep] this	6
23	it is [not/n't] [prep] this	6
24	it is precisely [prep] this	6
25	it is precisely [prep] this	6
26	it is helpful [prep] this	6
27	it is helpful [prep] this	6
28	it is [noun sg] [prep] this	6
29	it is not [prep] this	6
30	[conj] it is [prep] this	130