As you know,it is my duty to________my younger sisters from being hurt when they are in danger.
I might fail,but________I insist on doing it.I never lose heart.
—How did you pass the challenging test?—It was a long time________I found a series of suitable methods.
Because of H7N9 bird flu,all the chicken markets in Shanghai have been closed and won’t open until further________.
Hiking by oneself can be fun and good for health.It may also be good for________building.
I can not understand why the issue of Syria has become so complicated________I learn more from the media.