Which choices are included in the definition of "mass extinction"? A. The event must be global B. All ecologies must be involved C. The duration of the event must be short D. The number of species extinction must exceed 30% existing at the time

The definition of "mass extinction" includes the following choices:

A. The event must be global: This is true. A mass extinction event is not localized to a specific region or ecosystem. It affects life forms globally.

B. All ecologies must be involved: This is also true. Mass extinction is not limited to a specific type of ecology or habitat. It affects all types of life forms, regardless of their ecological niche.

C. The duration of the event must be short: This is not necessarily true. While many mass extinctions have occurred over relatively short geological timescales, the exact duration can vary. Some mass extinctions may occur over thousands or even millions of years.

D. The number of species extinction must exceed 30% existing at the time: This is generally true. While there is no exact percentage that defines a mass extinction, a significant and rapid reduction in biodiversity is a key characteristic. Most scientists agree that a mass extinction event involves the extinction of 75% or more of species in a relatively short geological time period.