well if the reaction is to produce ammonia through it should be exothermic reaction ...so it should be low temperature (but in practice high temp are used)
but according to your question its mentioned that it is an endothermic reaction so a high temperature would favour the production of ammonia
and coming to pressure ,we have less no. of molecules of ammonia ,so acc to Le Chatelier principle an increase in pressure would favour the reaction to go in the side with less no. of molecules(since P is inversely proportional to V)... there fore the reaction requires high pressures
Hence answer to your question(if the question is correct) is (c)high temperature and high pressure
but if its exothermic then it would be (b)low temperature and high pressure
Hope this answer satisfies you !!!