I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "An example of a decision problem is the following. The input is an arbitrary graph. The problem consists in deciding whether the given graph is connected, or not. The formal language associated with this decision problem is then the set of all connected graphs—of course, to obtain a precise definition of this language, one has to decide how graphs are encoded as binary strings."? 

What kind of definition of the language is desired?