Answer:
C. To find out if the call of an animal is missing
Explanation:
The more scientists listen to these kinds of recordings, the more they notice when an expected call is missing.
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Authors use characters to show the theme. The story is the outgrowth of the theme. If an author wants to write about love lasting forever, he may write a love story with two people who realize that they are going to die and find the fountain of youth, or something like that.
The principal structural characters effected were in the postcranial anatomy, especially in the skeletal and muscular systems.