The diagram below shows four columns that represent rocks from different geographic regions. Each layer within a column represents a brief period of time. Which of the four fossils would be the most useful as a reference to determine the age of newly discovered fossils? Why?

(A) fossil is the most useful.

It serves as an index fossil. The seashell is a great index fossil because it only appears in the sandstone layer in multiple locations in the same layer of time.

Explanation:

Index fossils are fossils used to define and identify geologic periods. Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends.

explanation:

on disadvantage of hydroelectric power is the cost. another disadvantage of using hydroelectric power is finding a water source powerful enough to harvest hydroelectric power.

if you add everything up correctly you should get 69 i got this because 50 plus 19 is it