单项选择题
A．The Greatest Killer in the West B．Heart Disease: Treat or Prevent C．Modern Technology and Heart Surgery D．Heart Surgery: Advantage and Disadvantages
A．more money should be spent on the prevention of heart disease B．heart surgery has helped most patients improve their conditions C．modern technology has made heart surgery more risky than before D．the public have known a great deal about the causes of heart disease
A．The environment of London is better than Toronto. B．In the first paragraph the underlined part means a modern and advance capital. C．Beijing is badly polluted mainly by coal burning. D．Liquefied gas is more expensive than petrol.