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

Answer: Option A

progress : develop towards an improved or more advanced condition.
thinking : the process of considering or reasoning about something.
efforts : a vigorous or determined attempt.
start : begin or be reckoned from a particular point in time or space; come into being.
headway : forward movement or progress, especially when this is slow or difficult.


Synonym of progress is headway