***urgent*** 40 points
how can earth’s layers be defined? select the two correct answers.
by their chemical compositions
by their asthenospheres
by their physical properties
by their proximities to the core
by their amounts of land area

The hershey and chase experiments involved the preparation of two different types of radioactively labeled phage. which of the following best explains why two preparations were required? a. the bacteriophage used in the experiments was a t2 phage. b. it was necessary that each of the two phage components, dna and protein, be identifiable upon recovery at the end of the experiment. c. each scientist had his own method for labeling phage, so each conducted the same experiment using a different isotope. d. establishing the identity of the genetic material required observation of two phage generations.