An edible sac fungus is

Options

A. Lycoperdon
B. Agaricus
C. Morchella
D. Rhizopus

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for an edible sac fungus. Sac fungi belong to the division Ascomycota, which is characterized by the formation of ascospores in a sac-like structure called an ascus.

2. **Analyzing the Options**:
- **Option 1: Lycoperdon**: This is a type of fungus commonly known as the earthball. It is indeed edible but belongs to the group of club fungi (Basidiomycota), not sac fungi (Ascomycota). Therefore, this option is incorrect.

- **Option 2: Agaricus**: This genus includes many edible mushrooms, such as the common button mushroom. However, Agaricus is also classified as a club fungus (Basidiomycota) and not a sac fungus. Hence, this option is also incorrect.

- **Option 3: Morchella**: This is the genus of morels, which are indeed edible and classified as sac fungi (Ascomycota). Morels have a distinctive honeycomb appearance and are considered a delicacy. Therefore, this option is correct.

- **Option 4: Rhizopus**: This genus includes molds that are often associated with food spoilage and can cause infections. Rhizopus is not edible and is not classified as a sac fungus. Thus, this option is incorrect.

3. **Conclusion**: After analyzing all the options, the correct answer to the question "An edible sac fungus is" is **Morchella**.

### Final Answer:
The edible sac fungus is **Morchella**.

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