Of the following, the most recent ancestors of vascular plants were probably :

Options

A. mosses
B. red algae
C. horsetails
D. green algae

Explanation

To determine the most recent ancestors of vascular plants from the given options, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Vascular Plants**:
- Vascular plants are characterized by the presence of vascular tissues, specifically xylem and phloem, which are essential for the transport of water, nutrients, and food.

2. **Identify the Groups**:
- The options provided are:
- Mosses
- Red algae
- Horsetails
- Green algae

3. **Classify the Options**:
- **Mosses**: These are non-vascular plants belonging to the division Bryophyta. They do not have xylem and phloem.
- **Red Algae**: These are also non-vascular plants and do not possess vascular tissues.
- **Horsetails**: These belong to the division Pteridophyta, which includes vascular plants. They have xylem and phloem.
- **Green Algae**: While some green algae are more closely related to land plants, they are still considered non-vascular.

4. **Determine the Most Recent Ancestor**:
- Since horsetails are part of the vascular plants and are classified under Pteridophyta, they are the most recent ancestors of vascular plants. The other options (mosses, red algae, and green algae) do not have vascular tissues and are therefore not considered ancestors of vascular plants.

5. **Conclusion**:
- The most recent ancestors of vascular plants from the options given are **Horsetails**.

### Final Answer:
**Horsetails** are the most recent ancestors of vascular plants.

---