A dioecious plant is

Options

A. Pinus
B. Maize
C. Cycas
D. Chara.

Answer

To answer the question "A dioecious plant is", we need to understand the definition and characteristics of dioecious plants.

### Step-by-Step Solution:

1. **Definition of Dioecious Plants**:
- Dioecious plants are those that have distinct male and female individuals. This means that one plant will produce only male gametes (pollen), while another separate plant will produce only female gametes (ovules).

2. **Examples of Dioecious Plants**:
- Common examples of dioecious plants include holly, kiwifruit, and certain species of willows. However, in the context of the options given in the question, we need to identify which one fits.

3. **Analyzing the Options**:
- **Option A: Spinus** - This is not a recognized dioecious plant.
- **Option B: Mace** - This does not refer to a dioecious plant.
- **Option C: Cycus** - This is a genus of plants known to be dioecious. Male and female Cycus plants are separate, with males producing pollen and females producing seeds.
- **Option D: Chara** - This is a green algae and is typically monoecious, meaning it has both male and female reproductive structures on the same individual.

4. **Conclusion**:
- Based on the definitions and analysis of the options, the correct answer is **Option C: Cycus**. This plant exhibits dioecious characteristics as it has separate male and female plants.

### Final Answer:
A dioecious plant is **C: Cycus**.