The correct answer is option 'A': invasive species.

Explanation:
An invasive species is a non-native species that is introduced to a new environment and has the potential to cause harm to the native species, ecosystems, or human activities in that area. The Caribbean false mussel (Mytilopsis sallei) is an example of an invasive species.

Invasive Species:
Invasive species can have significant negative impacts on ecosystems and biodiversity. They often outcompete native species for resources such as food, space, and habitat, leading to a decline in the native species population. Invasive species can also disrupt the natural balance of ecosystems, alter habitats, and cause economic damage.

Invasive species are typically introduced to new areas through human activities, such as international trade, travel, or accidental transportation. They may be unintentionally transported as stowaways in shipping containers, on boats, or attached to the hulls of ships. Once introduced to a new environment, invasive species can spread rapidly due to their ability to adapt and reproduce quickly.

Caribbean False Mussel:
The Caribbean false mussel (Mytilopsis sallei) is a small bivalve mollusk that is native to the Caribbean region. It is also known as the "brackish-water mussel" or "false dark mussel." This species is typically found in brackish water habitats, such as estuaries, lagoons, and mangrove forests.

The Caribbean false mussel has been introduced to several regions outside its native range, including the Gulf of Mexico, the Atlantic coast of the United States, and the Mediterranean Sea. Once introduced, it can rapidly colonize new areas and outcompete native mussel species. This can have negative impacts on the biodiversity and ecological balance of the invaded ecosystems.

The Caribbean false mussel has a high reproductive capacity, and its larvae can be easily transported by water currents, facilitating its spread to new areas. It can also attach itself to various substrates, including rocks, shells, and man-made structures, further aiding its colonization.

Control and Management:
Controlling invasive species like the Caribbean false mussel is challenging once they become established in a new environment. Strategies for managing invasive species include early detection and rapid response, prevention of further introductions, and targeted removal or control measures. It is important to raise awareness about the potential impacts of invasive species and take steps to prevent their introduction and spread.

In conclusion, the Caribbean false mussel is classified as an invasive species because it is a non-native species that has been introduced to new areas outside its native range and has the potential to cause harm to native species and ecosystems.