The correct answer is - A. widening.
Both of the countries suffer from low fertility rate, Japan little more than the USA. The gap is widening because of the migrations.
- USA is country that is on the top of the list as a destination for migration, and also it is a country that allows big number of migrants in it every year, that contributes to the country's population to become bigger and bigger even though the fertility rate is low.
-Japan the other hand is a country that has both very low fertility rate, and very small amount of migrants coming to live in it, so the number of the population is stagnant for some time now, and is expected to start decreasing quickly in the coming years once the older population is not among the living anymore.
The correct answer is - C. Volcanic derived carbon dioxide gas bubbled from the lake and suffocated people and animals nearby.
In the summer of 1986, more specifically on the August 21st, a big tragedy happened in Cameroon. The Lake Nyos, located in the northwestern part of the country experienced a limnic eruption. This eruption triggered the release of very large amounts of carbon dioxide from the lake. The exact amount of carbon dioxide that was released is debatable, and the general consensus is that it was between 100,000 and 300,000 tons of the gas, though there are suggestions that it was up to 1.6 million tons.
The gas spread around very quickly, and being heavier than the air it stuck very low. In a radius of around 25 km from the lake, lot of people and animals were suffocated. The estimates are that 1746 people died and around 3,500 livestock died, not even counting the damage that has been done to the wild animals.
I would say that the US and the Soviet Union at the end of WWII withdrew their troops as soon as a demilitarized zone was created. Also, I am sure they would require a peace treaty to be signed with Germany before withdrawing troops.
The construction and operation of dams in the Colorado River have multiple benefits that include having increased water for irrigation and domestic supply, generation of hydroelectric power energy, providing improved aquatic recreation and wildlife habitat, and flood control.
