In the Meselson-Stahl experiment, if the semiconservative model was correct, what was the expected composition of DNA molecules after two rounds of replication

Which sentence best expresses the differing opinions of these two book reviews?

One statements is an example of a scientific observation. another statement is an example of a scientific explanation. identify the correct statement for each category to illustrate how scientific explanations are inferred from scientific observations.

Each pair of clay balls represents two planetesimals. if each planetesimal is composed of the same material and is separated he the same distance, which pair experiences the frayed gravitational attraction?