Read this article, then choose the only alternative that is correct from A-D to fill each numbered gap.

THE BEGINNINGS OF FLIGHT

The story of man’s mastery of the air is almost as old as man himself, a puzzle in which the essential clues were not found until a very late stage. However, to __________ (36) this we must first go back to the time when primitive man __________ (37) his food, and only birds and insects flew. We cannot know with any certainty when man first deliberately shaped weapons for throwing, but that __________ (38) of conscious design marked the first step on a road that __________ (39) from the spear and the arrow to the airplane and the giant rocket of present __________ (40). It would seem, in fact, that this __________ (41) to throw things is one of the most primitive and deep-seated of our instincts, __________ (42) in childhood and persisting into old age. The more mature ambition to throw things swiftly and accurately, which is the origin of most outdoor games, probably has its roots in the ages when the possession of a __________ (43) weapon and the ability to throw it with force and accuracy __________ (44) the difference between eating and starving.