In my experience it's a combination of b) and c): most of the added value is generated by a surprisingly small number of "heroes" and everyone else is just ther

In my experience it's a combination of b) and c): most of the added value is generated by a surprisingly small number of "heroes" and everyone else is just there to support them. While the random office drone's contribution to the project's success is small, the fact that none of the "heroes" had to bother spending time and effort on that little side task enabled the team as a whole to solve the difficult issues quicker.