The Cambrian explosion occurred primarily in the oceans.The first challenges that had to be overcome during the mass colonization of dry land in the Ordovician period were

A) support of body structure without buoyancy in water, movement, and reproduction.
B) photosynthesis, cellular respiration, and reproduction.
C) DNA replication, photosynthesis, and cellular respiration.
D) DNA replication, phagocytosis, and cellular respiration.