That doesn't make a lot of sense! The only way the controller would know if the pilot told him or the appropriate Mode A was set. I would suggest the question is wrong or based on some very old equipment, where auto decoder (plot extractor?) could interpret the pulse replies of the Mode A and display a value - but without a code callsign conversion to convert the Mode A to a meaningful callsign.
Interpreting the question differently could be "The radar controller suspects that you are experiencing unlawful interference. What should he do to confirm this on his display system (without callsign conversion)?
The answer would be to check the Mode A is 7500 - the unlawful interference Mode A code. I don't understand the change from 7500 to 7700 in the answer.
RS