I don’t understand this question

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

The fruit of a certain plant is sweet and fleshy. the seeds of this plant have a seed coat that is fairly tough. the seeds germinate better if they are exposed to acid, or scarification. what is the most likely type of dispersal for this seed? water animal wind

Several billion years ago which gas was the least prevailant in the atmosphere