Inspite of their efforts, the team of scientists could not make much headway to solve the problem.

Answer: Option D

Results : a thing that is caused or produced by something else; a consequence or outcome.
Start : begin or be reckoned from a particular point in time or space; come into being.
Efforts : a vigorous or determined attempt.
Progress : forward or onward movement towards a destination.
Headway : forward movement or progress, especially when this is slow or difficult.

Synonym of Headway is Progress