1)A sudden large increase in the number of people in an area is called a ................ . A. population explosion B. population crisis C. population increase D. population growth 2)China’s population growth rate has ................ in the past years, although its population is still ................ A. declined – decreasing B. dounled – increasing C. increased – decreasing D. decreased – increasing 3)It has been predicted that the world’s population might reach the ................ of about 7 billion. A. figure B. amount C. quantity D. totality 4A ............... is a number representing a particular amount, especially one given in official information. A. image B. digit C. key D. figure 5)To ............... is to become, or make something become, twice as much or as many. A. double B. increase C. decrease D. rise up