**Core Concept**
The question is testing the understanding of graphical representations used in statistics to display the frequency distribution of continuous variables. A continuous variable is a quantity that can take any value within a given range or interval, such as height, weight, or blood pressure.

**Why the Correct Answer is Right**
The histogram is the best graphic representation of frequency distribution for a continuous variable because it uses bars of varying widths to represent the frequency of data points within each interval. This allows for a clear visualization of the distribution of data, including the shape, central tendency, and dispersion of the data. A histogram can reveal patterns such as skewness, outliers, and multimodality.

**Why Each Wrong Option is Incorrect**
**Option A:** A scatter plot is used to display the relationship between two variables, not the frequency distribution of a single variable.
**Option B:** A bar chart can be used to display categorical data, but it is not suitable for continuous data, which requires a more granular representation.
**Option C:** A line graph is used to display trends over time or across categories, but it is not the best choice for representing the frequency distribution of a continuous variable.

**Clinical Pearl / High-Yield Fact**
Remember, when dealing with continuous data, a histogram is often the most effective graphic representation for understanding the distribution of data, including its shape, central tendency, and dispersion.

**Correct Answer:** C. Histogram.