@chauhansunil20th Here we've been asked to find the "minimum" number of edges that is required to be removed so that we can get at least 2 connected components(so that we can say that graph is disconnected).
Now a $K_{10}$ graph will have all it's vertices have degree 9. Let's choose any vertex out of the 10 possibilities.
Now this vertex is connected to 9 other vertices . Only if i remove all the 9 edges , then I can guarantee that I will get two connected components right . A $K_{9}$ graph and one vertex. Otherwise , if less than 9 edges are removed , then there will be at least one edge that will keep the structure binded.
Thus , with removal of 9 edges associated to a particular vertex , we can guarantee that we'll get a disconnected graph.
This is also known as Edge connectivity.
Edge connectivity <=(Min degree of a graph)