Which of the following is haploid ?

Options

A. Primary spermatocytes and primary oocytes
B. Secondary spermatocytes and sec. oocytes
C. Spermatogonia and oogonia
D. Germinal cells.

Answer

To determine which of the following options is haploid, we need to analyze the ploidy level of each type of cell mentioned in the options provided.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Haploid (n)**: Cells that contain one complete set of chromosomes (e.g., gametes).
- **Diploid (2n)**: Cells that contain two complete sets of chromosomes (e.g., somatic cells).

2. **Analyze the Options**:
- **Option A: Primary Spermatocytes and Primary Oocytes**:
- Primary spermatocytes are formed from spermatogonia through mitosis and are diploid (2n).
- Primary oocytes are formed from oogonia through mitosis and are also diploid (2n).
- **Conclusion**: Both are diploid, so this option is incorrect.

- **Option B: Secondary Spermatocytes and Secondary Oocytes**:
- Secondary spermatocytes are formed from primary spermatocytes through meiosis, resulting in haploid cells (n).
- Secondary oocytes are formed from primary oocytes through meiosis, also resulting in haploid cells (n).
- **Conclusion**: Both are haploid, so this option is correct.

- **Option C: Spermatogonia and Oogonia**:
- Spermatogonia are the precursor cells for sperm and are diploid (2n).
- Oogonia are the precursor cells for eggs and are also diploid (2n).
- **Conclusion**: Both are diploid, so this option is incorrect.

- **Option D: Germinal Cells**:
- Germinal cells refer to the precursor cells (spermatogonia and oogonia) and are diploid (2n).
- **Conclusion**: This option is also incorrect.

3. **Final Answer**:
- The only option that contains haploid cells is **Option B: Secondary Spermatocytes and Secondary Oocytes**.