Variable would be the most logical
C. Organ System
Like said in the definition above, an organ system is a group of organs working together to perform a specific function for the organism.
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Answer:
The esophagus.
Explanation:
Which is a long tube that connects the mouth to the stomach
Answer:
Respiratory system and circulatory system.
The respiratory system allow living things to obtain oxygen from the air while the circulatory system allows oxygen to be carried around the body.
They drill holes and bring up samples of rock and study how seismic wave move through the earth.
