Development which freed land vertebrates from water was

Options

A. four appendages
B. four chambered heart
C. cleidoic eggs
D. lungs

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about a significant development that allowed land vertebrates to evolve from aquatic environments.

2. **Identifying Key Developments**: In the evolution of vertebrates, several key adaptations have occurred, but we need to focus on the one that specifically allowed for the transition from water to land.

3. **Recognizing the Importance of Eggs**: One of the major developments in this transition is the evolution of eggs. Specifically, the development of shelled eggs, also known as cleidoic eggs, played a crucial role.

4. **Defining Cleidoic Eggs**: Cleidoic eggs are eggs that have a protective shell. This adaptation allows the eggs to be laid on land without the risk of drying out, which is a significant advantage over eggs that must be laid in water.

5. **Impact on Reproductive Strategy**: With the ability to lay eggs on land, vertebrates no longer needed to return to water for reproduction. This adaptation eliminated the vulnerable tadpole stage, which is a delicate phase in the life cycle of many aquatic vertebrates.

6. **Conclusion**: The evolution of cleidoic eggs was a pivotal development that freed land vertebrates from their dependence on water for reproduction, allowing them to thrive in terrestrial environments.

7. **Final Answer**: The development that freed land vertebrates from water was the evolution of cleidoic eggs.