The system regarding the use of conjunctive is the same
independent of the fact that the phrase in question
might be a question. If the question has an interrogative
pronoun (see chapter
28) then the interrogative pronoun is used also
in the subordinate clause of the reported speech. Is
there no interrogative pronoun the subordinate clause
starts with the conjunction ob.
Actually the system is similar to the English as you
can see in the following examples.