Question

Sea mounts with flat-topped profiles are called _____.
A- Atolls
B- Guyot
C- Ridge
D- None of these

Answer 1

Hint:
A seamount is a mountain formed by volcanic activity that is underwater. These flat summits can have a diameter of more than 10 km (6.2 mi). In the Pacific Ocean, they are most commonly present, but in all oceans except the Arctic Ocean, they have been recorded.

Complete answer:
A Guyot, also known as a table mount, is an isolated volcanic underwater mountain (seamount) in marine geology with a flat top more than 200 m (660 ft) below the sea surface.

When above the sea, Guyots show signs of gradual subsidence across stages from fringed reefed mountains, coral atolls, and finally a flat-topped submerged peak.

Seamounts are formed in phases by extruding lavas piped upwards from sources within the mantle of the Earth, typically hotspots, to vents on the seafloor. After a while, volcanism inevitably stops, and other processes dominate. Wave action and/or coral reef construction appear to create a flat-topped edifice when an undersea volcano grows high enough to be near or breach the ocean surface. However, from hot magma and/or rock, which cools over time, all ocean crust and guyots form. As the lithosphere on which the future guyot rides slowly cools, through the isostasy process, it becomes denser and sinks lower into the mantle of the Earth. Furthermore the erosive effects of waves and currents are often found near the surface: below this higher erosion region, the tops of guyots typically lie.

Therefore the correct answer is B

Note
A ring-shaped coral reef, with a coral rim that partially or completely surrounds a lagoon, is an atoll.

A ridge or ridge of a mountain is a geographical feature consisting of a chain of mountains or hills that for some distance form a continuous elevated crest.