SN4 ""

No	Pattern	Freq
1	it is very difficult	227
2	it is extremely difficult	81
3	it is more difficult	76
4	it is often difficult	69
5	it is sometimes difficult	29
6	it is always difficult	24
7	it is also difficult	20
8	it is so difficult	16
9	it is quite difficult	16
10	it is notoriously difficult	15
11	it is increasingly difficult	15
12	it is still difficult	12
13	it is rather difficult	11
14	it is therefore difficult	10
15	it is particularly difficult	9
16	it is usually difficult	7
17	it is too difficult	7
18	it is equally difficult	5
19	it is obviously difficult	5
20	it is especially difficult	5
21	it is surprisingly difficult	5