Jessica is worrying about ______ she has passed the exam.
Scientists say it may be five or six years _______ it is possible to test this medicine on human patients.
More and more people have got to know the importance of the English study. ______, about six people in ten in this city are able to speak a little English.
It is only ______ you understand what your parents do to you ______ you can improve your relationship with your parents.
---When did you get to know each other ? ----It was in 2008___ we spent summer vocation together.
Many parents have called head teachers to know ______ their children are getting along well with everything in the school.