The Mass Extinction During Late Devonian, Which Is Related to Global

The mass extinction during Late Devonian, which is related to global collapse of the coral-strome reef systems and loss of other prominent taxa, was caused largely by

A) an unexplained short-term dimming of the Sun.
B) formation of Earth's first widespread forests.
C) glaciers spreading over a portion of southern Gondwanaland.
D) global warming due to injection of carbon dioxide into the atmosphere.