Answer:
D. They define geological periods because scientists use them as reference points for tracking the history of the earth.
Explanation:
Catastrophic events related to changes in geological timeline are very useful in defining geological periods.
These events have very significant appearance in the geological record and can be used to determine the history of the earth.
The catastrophic events usually culminates into extinction cycles or termination of some organisms from the earth surface.
Geologists use these events that are often wide spread to delineate geological periods.
Answer:
Astraphobia, also known as brontophobia, is a kind of phobia characterized by an intense fear of extremely loud but natural noises in the environment. Namely, lightning and thunder.
A. (Please mark brainliest)
Cardiac muscle is one of the three major muscle types, the others being skeletal and smooth. Some cardiac muscle cells are auto-rhythmic. They contract even in the absence of neuronal innervation. Intercalated disks are located between cardiac muscle cells.
An individual animal, plant, or single-celled life form. ;)
