In human females, an event that reflects onset of reproductive phase is

Options

A. growth of body
B. changes in hair pattern
C. change in voice
D. menstruation

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about an event that signifies the onset of the reproductive phase in human females.

2. **Identifying Key Events**: In human females, several changes occur during puberty that indicate the beginning of reproductive capability. These include:
- Growth of the body
- Change in hair patterns
- Change in voice
- Menstruation

3. **Analyzing the Options**: Among the listed options, menstruation is the most significant event that indicates the onset of the reproductive phase. It is a biological process that occurs monthly and is associated with the reproductive system.

4. **Defining Menstruation**: Menstruation is the monthly shedding of the uterine lining (endometrium) when there is no fertilization of an egg. It typically begins in girls between the ages of 11 to 13 years.

5. **Understanding the Menstrual Cycle**: The menstrual cycle lasts about 28 days, with ovulation occurring around the 14th day, where a mature egg is released from the ovary.

6. **Conclusion**: The event that reflects the onset of the reproductive phase in human females is menstruation.

### Final Answer:
**Menstruation**

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