A scatter plot would be best for non-related data points. A line graph would be best for related data points.
When the data on the graph is continuous,it does make sense to connect the points on the graph of 2 related variables.
They make points in space related to each other. Now they are connected in the problem, instead of just points on the graph.
A discrete graph.
It depends on what you are trying to do.
either a scatter graph or a line graph xx :)
A Linear graph
Not linearly related.