This line chart displays the median PM 2.5 concentration for each month of the year, using a smooth basis curve to connect data points. The visualization, built with D3 v5, employs `scaleLinear` for both axes and `axisBottom`/`axisLeft` for tick marks. Data is loaded via `csv` from a GitHub gist, with month names converted to numbers. The chart includes labeled axes for "Month" and "Median PM 2.5 Conc," rendered as an SVG with a styled path.