"This is a difficult question."
Translation:यह एक मुश्किल सवाल है।
A bit of a shot in the dark, but I think यह मुश्किल सवाल है। could also be understood to mean "There is this difficult question", as in:
"तुम क्या सोच रहे हो? कुछ problem है?"
"यह मुश्किल सवाल है।"
What are you thinking? Is there some problem?
There is this difficult question (that must be addressed).