The motile asexual reproductive unit is called:

Options

A. Zoospore
B. Aplanospore
C. Zygospore
D. Microspore

Explanation

To solve the question "The motile asexual reproductive unit is called:", we will analyze the given options step by step.

### Step-by-Step Solution:

1. **Understanding the Question**:
- The question is asking for the name of a motile asexual reproductive unit. This means we are looking for a type of spore or reproductive structure that can move and is involved in asexual reproduction.

2. **Analyzing the Options**:
- **Option 1: Zoospores**:
- Zoospores are a type of motile asexual spore that can swim using flagella. They are commonly found in certain algae and fungi. For example, the green alga Chlamydomonas reproduces asexually through zoospores. This option seems correct.

- **Option 2: Aplanospores**:
- Aplanospores are non-motile asexual spores. Since the question specifically asks for motile spores, this option is incorrect.

- **Option 3: Zygospore**:
- Zygospores are thick-walled resting spores formed by the fusion of two haploid cells. They are not motile and are involved in sexual reproduction, making this option incorrect.

- **Option 4: Microspore**:
- Microspores are small spores that develop into male gametophytes in plants. They are not motile and are involved in sexual reproduction, so this option is also incorrect.

3. **Conclusion**:
- After analyzing all the options, the only motile asexual reproductive unit is **zoospores**. Therefore, the correct answer is **Option 1: Zoospores**.

### Final Answer:
The motile asexual reproductive unit is called **zoospores**.

---