Flat-topped submerged volcanic mountains that show evidence of gradual subsidence below sea level are known as:

In which geographical area is the world's largest accumulation of marine plastic debris, known as the Great Pacific Garbage Patch, located?

Consider the following pairs: Oceanic Trench — Ocean I. Mariana Trench — Pacific Ocean II. Tonga Trench — Indian Ocean III. Peru-Chile Trench — Pacific Ocean IV. Puerto Rico Trench — Atlantic Ocean How many of the above pairs are incorrectly matched?