In geology, a key bed (syn marker bed) is a relatively thin layer of sedimentary
rock that is readily recognized on the basis of either its distinct
physical characteristics or fossil content and can be mapped over a very
large geographic area.[1]
As a result, a key bed is useful for correlating sequences of
sedimentary rocks over a large area. Typically, key beds were created as
the result of either instantaneous events or (geologically speaking)
very short episodes of the widespread deposition of a specific types of sediment. As the result, key beds often can be used for both mapping and correlating sedimentary rocks and dating them. Volcanic ash beds ( and bentonite beds) and impact spherule beds, and specific megaturbidites
are types of key beds created by instantaneous events. The widespread
accumulation of distinctive sediments over a geologically short period
of time have created key beds in the form of peat beds, coal beds, shell beds, marine bands, black in cyclothems, and oil shales. A well-known example of a key bed is the global layer of iridium-rich impact ejecta that marks the Cretaceous–Paleogene boundary (K–T boundary). Please let me know if it works.
Answer:
The correct answer is "the induced fit model".
Explanation:
The first model that looked to explain the enzyme and substrate interaction was the "lock and key" model. Although this model helped scientists to understand the specificity nature of the interaction enzyme-substrate, it does not reflect reality since enzyme was portrayed as a lock with a structure that doesn't change during the catalysis. Then half century later "The induced-fit theory" was proposed which fits much better the newer version of the enzyme action model. In this theory the enzyme is partially flexible and its structure changes as a result of its interaction with the substrate.
B, because it's not an advantage for something to be expensive and time consuming
