20. When the blood enters the gill filaments in a fish, its carbon dioxide content is ________ and oxygen content is _____

a. low;high
b. low;low
c. high;high
d. high;low
D? I'm not sure about this question...

Thanks
-MC

Thanks

-MC

To determine the answer to this question, let's understand the process of gas exchange in fish gills.

Fish use their gills to extract oxygen from the water and eliminate carbon dioxide. As water flows over the gill filaments, oxygen diffuses into the blood while carbon dioxide diffuses out of the blood. Therefore, when the blood enters the gill filaments, its carbon dioxide content is high, as it needs to dispose of the waste carbon dioxide.

On the other hand, the oxygen content in the water is higher than in the blood, so oxygen diffuses from the water into the bloodstream across the gill filaments. This means that the blood's oxygen content becomes high after passing through the gill filaments.

Based on this information, the correct answer is:

d. high; low

The blood entering the gill filaments in a fish has a high carbon dioxide content and a low oxygen content.