A line chart tracks cumulative global COVID-19 deaths over time, using a black marker line to highlight the point where the death toll reaches three million. The visualization loads time-series data from the Johns Hopkins CSSE repository via `d3.csv`, transforms dates with `d3.timeParse`, and renders an SVG path generated with `d3.line`. Scales are created with `d3.scaleTime` and `d3.scaleLinear`, while React manages the component state and updates the chart.