Bacteriophages are viruses that infect bacteria. In an experiment, bacteriophages were labeled with either radioactive phosphorus or radioactive sulfur. The labeled bacteriophages were incubated with bacteria for a brief amount of time and then removed. The infected bacteria cells were found to contain significant amounts of radioactive phosphorus but not radioactive sulfur. Based on the results of the experiment, which of the following types of molecules did the bacteriophages most likely inject into the bacteria cells.

The right answer is DNA

Explanation:

Bacteriophage is a virus that infects its host which are bacteria. These have genetic material which are enclosed in the proteinaceous coat. Protein contains a large amount of sulfur and DNA contains a large amount of phosphorus in it.

So when the bacteriophage labeled with radioactive phosphorus and sulfur infected bacteria the infected bacteria were found to contain significant amounts of radioactive phosphorus, not sulfur which shows that DNA got transferred into the bacteria not proteins because DNA was labeled with radioactive phosphorus.

So DNA would be the molecules that the bacteriophage most likely to inject into the bacterial cell.