It is such a difficult problem that I can't explain it
All the houses in the neighborhood have been destroyed by the fire
If he took my advice, he wouldn't get into trouble
How long have you learnt English?
9.It is such a difficult problem that I can't explain it
10.All the houses in the neighborhood have been destroyed by the fire
11.If he took my advice, he wouldn't get into trouble
12.How long have you learnt English ?