Answer :
The author's purpose in this passage from "The Race to Space: Countdown to Liftoff" is most likely:
- To add supplemental information that explains the situation.
In this passage, the author provides information about NASA absorbing different entities like NACA, Caltech's Jet Propulsion Laboratory, and the army's rocket-research team. This additional information helps the reader understand the background and context of how NASA came to be and the resources it brought together to advance space exploration. By including these details, the author enhances the reader's understanding of the historical development of NASA and its significance in the race to space.