Read the passage and choose the best answer for each question

Different regions have different rates of population growth, but in the 20^th century, the world saw the biggest increase in its population in human history due to medical advances and massive increase in agricultural productivity made by the Green Revolution.

However, in some countries there is a negative population growth, especially in the Central and Eastern Europe, mainly due to low fertility rate ,and Southern Africa due to the high number of HIV – related deaths .Within the next decades, Japan and some countries in Western Europe are also expected to encounter a negative population growth due to sub-replacement fertility rates .

Population growth which exceeds the carrying capacity of an area will result in overpopulation. On the contrary, such areas may be considered “under-populated” if the population is not large enough to maintain an economic system.