Living Foraminiferans Have Been Found at the Deepest Depth of the World's

Living foraminiferans have been found at the deepest depth of the world's oceans—10,896 m down in the Western Pacific's Challenger Deep.What explains why foraminiferans cannot secrete normal shells at these depths?

A) There is insufficient sunlight for photosynthesis.
B) There is insufficient calcium carbonate in the surrounding water.
C) It is too deep for coral animals.
D) There is insufficient silica in the surrounding water.
E) There is not enough organic matter to scavenge as an energy source for foraminiferans to build their shells.