I found this problem in a textbook with no answer provided:
Consider a graph G.
Do all subgraphs of G have to be either induced or spanning?
My inclination is that they do not since
(a) An induced subgraph is obtained by deletion of nodes only
(b) A spanning subgraph is obtained by deletion of edges only
Create a subgraph by deletion of one node and one edge. This is neither spanning nor induced.
Is this correct?