In an ascocarp:

Options

A. there are fertile and sterile hyphae
B. hyphae fuse, forming the dikaryotic stage
C. a sperm fertilizes an egg
D. hyphae do not have chitinous walls

Explanation

To answer the question regarding the characteristics of an ascocarp, we will analyze each option provided and determine which one is correct based on our understanding of Ascomycetes fungi.

### Step-by-Step Solution:

1. **Understanding Ascocarp**: Ascocarp is the fruiting body of fungi belonging to the Ascomycetes group. It is important to know that this structure is involved in the reproduction of these fungi.

2. **Analyzing Option A**: The first option states that there are fertile and sterile hyphae. In Ascomycetes, it is indeed true that both types of hyphae exist. Fertile hyphae are capable of reproduction, while sterile hyphae do not contribute to reproduction. This option seems plausible.

3. **Analyzing Option B**: The second option claims that hyphae fuse to form the dikaryotic stage. However, in Ascomycetes, it is the fusion of male and female gametes that leads to the dikaryotic stage, not the hyphae themselves. Therefore, this option is incorrect.

4. **Analyzing Option C**: The third option suggests that a sperm fertilizes an egg. This is misleading because fungi, including Ascomycetes, do not have sperm and eggs in the traditional sense. Instead, they have gametes that fuse during reproduction. Thus, this option is also incorrect.

5. **Analyzing Option D**: The fourth option states that hyphae do not have chitinous walls. This is incorrect because all fungal hyphae, including those in Ascomycetes, have cell walls made of chitin.

6. **Conclusion**: After analyzing all the options, we find that the only correct statement is Option A, which states that there are fertile and sterile hyphae present in an ascocarp.

### Final Answer:
The correct answer is **Option A: There are fertile and sterile hyphae.**

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