He labeled the protein of bacteriophages with radioactive sulfur and their DNA with radioactive phosphorus. The bacteriophages were allowed to infect bacteria.
The correct answer is option b, that is, the addition of carbon dioxide to the atmosphere.
If the concentration of carbon dioxide upsurges in the atmosphere due to the enhanced rate of outgassing, there will be a constant elevation in the global temperature. The elevating temperature and more dissolved carbon dioxide will result in enhanced weathering of crystal rocks as a consequence of faster rate of reactions and greater acidity.
