Tom, clean up the broken glass _________ someone walks on it.
Since the time humankind started gardening, we _ _ to make our environment more beautiful.
All the books donated by the students from urban schools are said ________ to the students in the earthquake-stricken areas the other day.
We got near a garden, _________ owner sitting in it .
To tell you the truth, I think it is you, ________Mr. Smith, ________.
________ the global economy is showing signs of recovery, many developing countries are still suffering.