Why is the geological interval around 100 million years ago called the "cretaceous"?
a) the name refers to abundant deposits of marine limestone from the period, indicating higher sea levels. b) cretaceous means ancient?
c) it is named for a species of dinosaurs widespread at the time.
d) the mediterranean island of crete was formed during this period.
e) none of the answers are correct

Option (A)

Explanation:

The cretaceous period formed the last period of the Mesozoic era, marked by the occurrence of some distinct major events, and it began about 145 million years ago and ended by about 65 million years ago. The name Cretaceous is actually derived from the Latin word 'Creta' which means “chalk”. Chalk usually refers to the white colored, soft, powdery limestone rock that is primarily comprised of fossil shells. These are basically dominated by the calcite minerals.

By the end of this period, the dinosaurs were completely wiped out from the earth and the flowering plants started to evolve after the mass extinction event, which is commonly known as the Cretaceous-Tertiary boundary (K-T boundary).

Thus, the name Cretaceous was given because during this time period, there was abundant deposition of marine limestones (chalk), depicting that the sea level was comparatively higher than the present day.

Hence, the correct answer is option (A).