Seed plants are all

Options

A. heterosporous
B. dioecious
C. monoecious
D. homosporous.

Explanation

To answer the question "Seed plants are all," we need to analyze the options provided and understand the characteristics of seed plants.

### Step-by-Step Solution:

1. **Understanding Seed Plants**: Seed plants are a group of plants that reproduce through seeds. They include two major categories: gymnosperms (like conifers) and angiosperms (flowering plants).

2. **Identifying Key Terms**:
- **Heterospory**: This refers to the production of two different types of spores: megaspores (female) and microspores (male). This is a crucial feature in the reproductive cycle of seed plants.
- **Dioecious**: Refers to plant species where individual plants are either male or female.
- **Monoecious**: Refers to plant species where both male and female reproductive structures are present on the same plant.
- **Homospory**: Refers to the production of only one type of spore, which is not conducive to seed formation.

3. **Analyzing Options**:
- **Option 1: Heterosporous**: This is correct because seed plants are heterosporous, producing both megaspores and microspores, which is essential for seed development.
- **Option 2: Dioecious**: This is not universally true for all seed plants, as some can be monoecious.
- **Option 3: Monoecious**: Similar to dioecious, this does not apply to all seed plants.
- **Option 4: Homosporous**: This is incorrect as homospory does not lead to seed formation.

4. **Conclusion**: Based on the definitions and characteristics discussed, the correct answer is **Option 1: Heterosporous**.

### Final Answer:
Seed plants are all **heterosporous**.

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