Your answer is Puerto Rico for sure
I think the Answer to your question is d.
Astronomers can often identify a binary system that includes only one visible star by observing the effects on the dim star's what on its brighter companion, causing a 'wobble'.
In order to aid population growth, countries can provide more resources in advertising pro natalist policies and benefits. an example of this can be seen in countries that are trying to boost their populations such as germany, japan, and the netherlands.
The type of region described is an economic region because many of the goals of the EU have to do with trade, jobs, and the economy.