In Ulothrix, sexual reproduction is by

Options

A. isogamy
B. anisogamy
C. oogamy
D. conjugartion.

Explanation

**Step-by-Step Solution:**

1. **Identify the Organism**: The question asks about Ulothrix, which is a type of green alga.

2. **Classify the Organism**: Ulothrix belongs to the class Chlorophyceae, which includes green algae.

3. **Understand the Reproductive Method**: The question specifically inquires about the method of sexual reproduction in Ulothrix.

4. **Define the Type of Sexual Reproduction**: In Ulothrix, sexual reproduction occurs through a process known as isogamy.

5. **Explain Isogamy**: Isogamy is characterized by the production of gametes that are similar in shape and size. This means that both male and female gametes are indistinguishable from each other.

6. **Conclude the Answer**: Therefore, the sexual reproduction in Ulothrix occurs by the isogamous method.

**Final Answer**: In Ulothrix, sexual reproduction is by isogamous method, where both male and female gametes are of similar shape and size.

---