Human sperm was discovered by
(a) Leeuwenhoek
(b) Aristotle
(c) Graaf
(d) Pander

Options

A. Leeuwenhoek
B. Aristotle
C. Graaf
D. Pander

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks who discovered human sperm. We need to identify the correct individual from the given options.

2. **Reviewing the Options**:
- (a) Leeuwenhoek
- (b) Aristotle
- (c) Graaf
- (d) Pander

3. **Identifying the Correct Answer**:
- **Antony van Leeuwenhoek**: He is known for his contributions to microscopy and is credited with the first observation of human sperm in 1677. This makes option (a) the correct answer.
- **Aristotle**: He was a philosopher and biologist who contributed to the classification of organisms but did not discover human sperm. Therefore, option (b) is incorrect.
- **Graaf**: Regnier de Graaf is known for his work in reproductive anatomy but did not discover human sperm. Thus, option (c) is incorrect.
- **Pander**: Karl Ernst von Baer and Pander are associated with embryology but not with the discovery of human sperm. Hence, option (d) is also incorrect.

4. **Conclusion**: Based on the historical context and contributions, the correct answer to the question is (a) Leeuwenhoek.

### Final Answer:
(a) Leeuwenhoek

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