Body cavity with blood found in arthropods and molluscs is.........

Explanation

**Step-by-Step Solution:**

1. **Identify the Organisms**: The question refers to two groups of organisms: arthropods and molluscs. Both of these groups have a unique body cavity that contains blood.

2. **Define the Body Cavity**: In arthropods and molluscs, the body cavity that contains blood is known as the hemocoel.

3. **Explain Hemocoel**: The hemocoel is a type of body cavity that is filled with a fluid called hemolymph, which functions similarly to blood in vertebrates.

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