Pollen grain is

Options

A. highly reduced male gametophyte
B. well developed male gametophyte
C. highly reduced sporophyte
D. well developed female gametophyte

Answer

### Step-by-Step Solution:

1. **Understanding Pollen Grains**:
- Pollen grains are the male gametophytes in seed plants, specifically in gymnosperms and angiosperms. They are crucial for reproduction.

2. **Development from Microspores**:
- Pollen grains develop from microspores. Each microspore undergoes mitosis to form a pollen grain, which contains the male gametophyte.

3. **Characteristics of Male Gametophyte**:
- The male gametophyte within the pollen grain is highly reduced compared to the female gametophyte. It typically consists of only a few cells.

4. **Function of Pollen Grains**:
- The primary function of pollen grains is to produce sperm cells. These sperm cells are necessary for fertilization of the egg cell, leading to the formation of a zygote.

5. **Conclusion**:
- Based on the above points, we can conclude that pollen grain is a highly reduced male gametophyte. The other options regarding well-developed male gametophyte, well-developed sporophyte, and female gametophyte are incorrect.

### Final Answer:
Pollen grain is a highly reduced male gametophyte.

---