On which of the following facts does the method of periodic abstinence is based ?

Options

A. Ovulation occurs on about the `14^(th)` day of menstruction
B. Ovum remains alive for about 1-2 days
C. Sperms survive for about 3 days
D. all of these

Explanation

To answer the question regarding the method of periodic abstinence, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Menstrual Cycle**:
- The menstrual cycle typically lasts about 28 days, although it can vary among individuals. It includes several phases: the menstrual phase, follicular phase, ovulation, and luteal phase.

2. **Identifying Ovulation**:
- Ovulation usually occurs around the 14th day of the menstrual cycle. This is when the ovary releases an ovum (egg) into the fallopian tube.

3. **Survival of the Ovum**:
- Once released, the ovum has a limited lifespan of about 1 to 2 days. This means that it can be fertilized by sperm only within this time frame.

4. **Survival of Sperm**:
- Sperm can survive inside the female reproductive tract for about 3 days. This means that if sperm are present before ovulation, they can still fertilize the ovum when it is released.

5. **Application of Periodic Abstinence**:
- To effectively use the method of periodic abstinence, couples avoid sexual intercourse during the fertile window, which is typically from about the 10th to the 17th day of the menstrual cycle. This is when the chances of conception are highest due to the overlap of sperm survival and ovum availability.

6. **Conclusion**:
- The method of periodic abstinence is based on the understanding of the timing of ovulation, the lifespan of the ovum, and the survival of sperm. Therefore, the correct answer to the question is that the method is based on all of these facts.