SN4 ""

No	Pattern	Freq
1	it [is] often [adj] [verb]	201
2	it [is] often [adj] [to-vb]	199
3	it is often [adj] [verb]	189
4	it [is] often difficult [verb]	62
5	it [is] often possible [verb]	41
6	it [is] often necessary [verb]	21
7	it [is] often hard [verb]	14
8	it 's often [adj] [verb]	12
9	it [is] often useful [verb]	9
10	it [is] often [adj] tell	8
11	it [is] often impossible [verb]	8
12	it [is] often [adj] to tell	8
13	it [is] often [adj] to use	7
14	it [is] often [adj] use	7
15	it [is] often [adj] see	6
16	it [is] often [adj] to find	6
17	it [is] often helpful [verb]	6
18	it [is] often [adj] find	6
19	it [is] often [adj] to see	6
20	it [is] often [adj] know	5
21	it [is] often [adj] think	5
22	it [is] often [adj] to make	5
23	it [is] often [adj] to determine	5
24	it [is] often [adj] to think	5
25	it [is] often [adj] to know	5
26	it [is] often [adj] determine	5
27	it [is] often [adj] make	5
28	it [is] often preferable [verb]	5