**Core Concept**
The normal distribution curve is a probability distribution that describes the distribution of many naturally occurring phenomena. The standard deviation (SD) is a measure of the amount of variation or dispersion from the average. Understanding the area under the curve within a certain range is crucial in statistics and research.

**Why the Correct Answer is Right**
The area under the normal curve within ± 1 standard deviation (SD) from the mean is approximately 68.27%. This is because the normal distribution curve is symmetric around the mean, and the area under the curve within 1 SD from the mean represents about two-thirds of the total area under the curve. This is a fundamental concept in statistics and is often used in research to describe the distribution of data.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not correct because the area under the normal curve within ± 1 SD is not equal to 50%. While 50% of the data falls within 1 SD of the mean, the area under the curve is a continuous measure that represents the probability of a value falling within a certain range.

**Option B:** This option is not correct because the area under the normal curve within ± 1 SD is not equal to 80%. While the area within 1 SD is a significant portion of the total area, it is not equal to 80%.

**Option C:** This option is not correct because the area under the normal curve within ± 2 SD is approximately 95%, not 68.27%.

**Clinical Pearl / High-Yield Fact**
A useful mnemonic to remember the areas under the normal curve within a certain number of standard deviations is: 68.27% within 1 SD, 95% within 2 SD, and 99.7% within 3 SD.

**Correct Answer: C. 95%**