[判断题]机械操作须经专业培训并持证上岗,严禁酒后作业, 严禁拆除安全保护装置和安全警戒装置。
A.正确
B.错误

We can begin our discussion of "population as global issue" with what most persons mean when they discuss "the population problem": too many people on earth and a too rapid increase in the number added each year. The facts are not in dispute; it was quite right to employ the analogy that likened demographic growth to "a long, thin powder fuse that burns steadily and haltingly until it finally reaches the charge and explodes".
To understand the current situation, which is characterized by rapid increases in population, it is necessary to understand. the history of population trends. Rapid growth is a comparatively recent phenomenon. Looking back at the 8,000 years of demographic history, we find that populations have been virtually stable or growing very slightly for most of human history. For most of our ancestors, life was hard, often nasty, and very short. There was high fertility in most places, but this was usually b
A. A virtually stable or slightly decreasing period and then a sudden explosion of population.
B. A slow growth for a long time and then a period of rapid, dramatic increase.
C. Too many people on earth and a few rapid increase in the number added each year.
D. A long period when death rates exceed birthrates and then a short period with higher fertility and lower mortality.