Which of the following are haploid in nature?
I. Spermatids
II. Secondary spermatocytes
III. Spermatogonia
IV. Primary spermatocytes

Options

A. I, II, III, are correct
B. I and II are correct
C. II and IV are correct
D. I and III are correct

Answer

To determine which of the given options are haploid in nature, we will analyze each option based on the process of spermatogenesis.

### Step-by-Step Solution:

1. **Understanding Spermatogenesis**:
- Spermatogenesis is the process of sperm formation that occurs in the testes. It involves several stages of cell division and differentiation.

2. **Analyzing Each Option**:
- **I. Spermatids**:
- Spermatids are the result of the second meiotic division of secondary spermatocytes. They are haploid (n) because they have half the number of chromosomes compared to the original diploid cell.
- **Conclusion**: Spermatids are haploid.

- **II. Secondary Spermatocytes**:
- Secondary spermatocytes are formed from primary spermatocytes through the first meiotic division. They are also haploid (n) as they have undergone reduction division.
- **Conclusion**: Secondary spermatocytes are haploid.

- **III. Spermatogonia**:
- Spermatogonia are the initial germ cells that undergo mitosis to produce primary spermatocytes. They are diploid (2n) because they have the full set of chromosomes.
- **Conclusion**: Spermatogonia are diploid.

- **IV. Primary Spermatocytes**:
- Primary spermatocytes are formed from spermatogonia and are also diploid (2n). They undergo meiosis to form secondary spermatocytes.
- **Conclusion**: Primary spermatocytes are diploid.

3. **Final Evaluation**:
- From the analysis, we find that:
- **Haploid**: Spermatids (I) and Secondary Spermatocytes (II)
- **Diploid**: Spermatogonia (III) and Primary Spermatocytes (IV)

4. **Correct Answer**:
- The options that are haploid in nature are **I (Spermatids)** and **II (Secondary Spermatocytes)**.

### Final Answer:
The correct options that are haploid in nature are **I and II**.