Answer: Meselson & Stahl reasoned that these experiments showed that DNA replication was semi-conservative: the DNA strands separate and each makes a copy of itself, so that each daughter molecule comprises one "old" and one "new" strand. The semi-conservative model, in which each strand of DNA serves as a template to make a new, complementary strand, seemed most likely based on DNA's structure. ... From the patterns of DNA labeling they saw, Meselson and Stahl confirmed that DNA is replicated semi-conservatively.
C. Vegetation because even though cows are important, all life is and not just that species and then cars and factories are unnatural and would not be critical for the carbon cycle in nature.
