If relatively small carbonaceous chondrites from space were a significant source of Earth's original amino acids, then which two of these would have been most important in permitting their organic materials to survive impact with Earth?
I. Carbonaceous chondrites must contain no D-amino acids.
II. Earth's early atmosphere must have had little free oxygen.
III. The chondrites must have arrived on Earth before 4.2 billion years ago.
IV. Earth's early atmosphere must have been dense enough to dramatically slow the chondrites before they impacted.
V. The chondrites must have impacted land, rather than a large body of water.