I think everyone should donate blood _____ he is healthy because that’s a citizen’s responsibility.
Unemployment in USA is likely to remain high in 2011, and _______ for the next few years.
I didn’t make sense of _______poem until I read it _______ third time.
—He failed in the exam again. —He __________his teacher’s advice.
When firstto the market, these products enjoy great success.
It is uncertain ______ side effect the medicine will bring about, although about two thousand patients have taken it.