This interactive line plot displays eyeSight data over time, with a dropdown menu to toggle between the S and C data columns. Users can also append new data points via a form that accepts a year, S value, and C value, which are then added to the dataset and trigger a re-render. The visualization is built with D3 v5, using `csv` to load data, `scaleTime` for the x-axis, `scaleLinear` for the y-axis, and `transition().duration(1000)` to animate the line path update. The menu is constructed using a custom `dropdownMenu` component that appends `option` elements to a `select` element.