SN4 ""

No	Pattern	Freq
1	it [verb] when	279
2	it [vb past] when	132
3	it [vb -s] when	111
4	it do when	30
5	it happen when	24
6	it did when	19
7	it [vb infin] when	17
8	it mean when	16
9	it start when	16
10	it happened when	14
11	it have when	13
12	it started when	12
13	it begin when	10
14	it does when	10
15	it had when	10
16	it began when	10
17	it means when	9
18	it occur when	9
19	it came when	9
20	it come when	9
21	it [vb pp] when	8
22	it occurs when	7
23	it hurt when	6
24	it appear when	6
25	it happens when	6
26	it seems when	5
27	it says when	5
28	it seem when	5
29	it depend when	5
30	it [v-ing] when	5