— Why are the four students so happy?—______ in the science competition, they are awarded prize money totaling $ 20,000.
People are advised not to smoke at home, since passive smoking is ________ topeople around them. Which is Not proper for the blank?
He stumbled(绊倒)on the _______ ground and fell flat on his face.
Many students today suffer from ________ problems, since they are under too much pressure.
________ energy is generated from natural resources—such as sunlight, wind, rain, tides and so on.
Effective measures have been taken to prevent _______pollution.