This is the answer to this question in case y’all need it because it was very hard for me to find it.

The answer would be dogs.

The direction a chemical reaction occurs is represented by an arrow 

Ais the

the correct answer is: " ventricles " .

"recent advances in brain imaging have allowed clinicians to make scientifically useful comparisons in the relative size of the chambers in the brain that are filled with cerebrospinal fluid."

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these chambers are called ventricles .