Once the physical prototypes of the Saturn V rocket were built, they were launched without any astronauts aboard. These test flights did not go all the way to the Moon, but they allowed engineers to figure out how each piece of the rocket performed in flight. The picture below shows the launch of the second test flight of a Saturn V rocket.

The second Saturn V rocket test flight is launched from Kennedy Space Center on April 4, 1968.
During the second test flight, the Saturn V rocket performed well on some tests but failed other tests. For example, some of the engines, called J-2 engines, failed their tests. The J-2 engines shut off before they were supposed to and would not turn back on. If the J-2 engines did not work properly during a lunar mission, the rockets would not supply enough power to send the astronauts all the way to the Moon.
Engineers tested several physical prototypes of the Saturn V rocket before sending astronauts into space. What was the purpose of testing the physical prototypes? Select all that apply.