(2014·福建名校质量检查)The tanker，which was full of petrol，________and gave off heavy and dark flames the moment a truck knocked into it.

Now the air in our hometown is ___________than it was before. Something must be done.

(2012·衡阳高二检测) People often have the belief _______ a healthy environment and development cannot be possible at the same time, but this does not have to be true

_______ any other species, human populations are shaped by the usual forces of natural selection, like famine, disease or climate

The sales of houses in our city fell by 40 percent last month, 48 percent __________ we don’t count low-price houses provided for poor residents