**Core Concept**
The Rhythm Method, also known as the fertility awareness method, is a natural family planning technique that relies on tracking a woman's menstrual cycle to predict when ovulation occurs and when she is fertile. This method is based on the understanding that ovulation typically occurs 14 days before the start of the next menstrual period in a woman with a regular 28-day menstrual cycle.

**Why the Correct Answer is Right**
In a woman with a 28-day menstrual cycle, the safe period is calculated by subtracting 14 days from the start of her menstrual period. This is because ovulation usually occurs around day 14 of a 28-day cycle, and the egg remains fertile for about 24 hours after ovulation. Therefore, the safe period, also known as the infertile period, is from day 1 to day 14 of a 28-day menstrual cycle. This allows for a window of time when the woman is not fertile and can safely engage in unprotected sex without the risk of pregnancy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a specific calculation or timeframe for the safe period.

**Option B:** This option is incorrect because it suggests that the safe period starts on day 15, which is not accurate for a 28-day menstrual cycle.

**Option C:** This option is incorrect because it is not specific to a 28-day menstrual cycle and does not provide a clear calculation for the safe period.

**Clinical Pearl / High-Yield Fact**
To calculate the safe period, simply subtract 14 days from the start of your menstrual period. This method is not foolproof and may not be effective for women with irregular cycles or other reproductive health issues.

**Correct Answer: C. Day 1 to 14.**