Why are cells specialized?

According to the big bang theory, after the "bang," the universe remained dark until about  300,000 yearsone billion yearsthree minutesthree billion years  later, when neutral atoms began to form.

Most of the fossils found in virginia are in the coastal plain, valley, ridge, and appalachian plateau regions, best suggesting that these geographic provinces a) were once covered by seawater. b) are the oldest parts of virginia. c) have a great deal of karst topography. d) have large amounts of sedimentary rock.

Why reason best illustrates why hershey and chase chose to use viruses in their experiment?