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.
Answer:

Explanation:
Given

See attachment
Required
Find 
To do this, we make use of the following theorem
--- angle at the center and angle between two tangents add up to 180 (i.e. they are supplementary angles)
So, we have:

Collect like terms


Pacific Plate. The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres (40,000,000 sq mi), it is the largest tectonic plate. The Pacific Plate contains an interior hot spot forming the Hawaiian Islands.
If your question is literally how long they could remain without water, the answer is 1-2 days with major side effects, and 3-4 with certain death.
Answer:
298 million, give or take