You can make a connection, because the starting point on the circle is determined, then the end point is determined, and there will be no third point to extend a line. The law is that any graph can be connected if all the points are even points or at most there are only two singularities. These are simple problems of topological mathematics (so-called singularity: any vertex on a graph is singular if there are odd lines connected with it, and vice versa, it is even. Note: The number of points may or may not be odd, and there can only be two at most. Two odd numbers are too many to connect. If a square is all even ... for your question, of course, it can be connected in one stroke, and all the figures composed of circles are even.