Fish breathe with the help of gills which are richly supplied with blood vessels. The gills help the fish to

Options

A. take in oxygen from air
B. take in oxygen dissolved in water
C. absorb nutrients present in water
D. release waste substances in water

Answer

**Step-by-Step Solution:**

1. **Understanding the Function of Gills:**
- Fish breathe using gills, which are specialized organs located on either side of their head. Gills are designed to extract oxygen from water.

2. **The Process of Breathing in Fish:**
- Fish take in water through their mouths. This water then flows over the gills.

3. **Oxygen Extraction:**
- As water passes over the gills, the dissolved oxygen present in the water is absorbed into the blood vessels that are richly supplied in the gills.

4. **Transportation of Oxygen:**
- The oxygen absorbed by the blood is then transported to all parts of the fish's body, where it is used for respiration.

5. **Carbon Dioxide Removal:**
- Simultaneously, carbon dioxide (CO2), which is a waste product of respiration, is transferred from the blood to the gills and then expelled back into the water.

6. **Conclusion:**
- Therefore, the primary function of gills in fish is to help them take in oxygen that is dissolved in water.

**Final Answer:**
- The gills help the fish to **take in oxygen dissolved in water** (Option B).

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