12.We were very impressed by her effort to overcome difficulties.
13.My friends have studied English for fifteen years.
14.They haven't written to each other for five years.
15.He has learnt English since he was in grade 6.
16.I last visited the museum was three months ago.
17.Tom has been ill for three days.
18.We started working on this programme five years ago.
19.In 2008 our teacher began to teach extra classes for students with learning disabilities.
20.We have already created a resource room for talented students with learning disabilities since 2013.
21.We have won the UNESCO charity award three times since 2011.
