I assume that the question refers to the political affiliation of the Islands (They are Islands in the Mariana Trench, in the Pacific Ocean, south of Japan) - they are politically linked to the US - the correct answer is a). For example the Mariana islands have a commonwealth status within the US.
The Great Barrier Reef is the world's largest living structure. It is made up of around 2900 individual reefs and 900 islands. ... Climate change is perhaps the biggest threat to the Great Barrier Reef. Warmer ocean temperatures put stress on coral and lead to coral bleaching.
Chernozem is the right answer
You can easily google this.
