According to the Big Bang theory, the universe was once very dense and is now expanding.
The answer to your question is B.
The Hershey–Chase experiment was based on a bacteriophage T2 (a virus), to that DNA is the genetic material. Bacteriophage T2 attacks bacterium and makes its copies. Based on the experiment, Hershey and Chase deduced that it is the DNA of virus enters bacteria to make virus copies. To trace viral DNA, Hershey and Chase label DNA with ³²P (radioisotope of phosphorus) because phosphorus is not present in most of the proteins.
