Question

saving the apollo 13 mission
on april 11, 1970, apollo 13 was launched for a planned moon landing. two days into the mission, however, one of the oxygen tanks in the spacecraft exploded, causing a loss of air, electricity, and water. the moon landing had to be canceled, and the astronauts had to figure out how to get home. their solution was to move into the lunar module, the small craft that was supposed to land on the moon, for much of the remaining trip. the lunar module contained fewer supplies, however. therefore, the astronauts had to conserve as much food and water as possible. by firing the lunar modules engine, the men were able to get the spacecraft on the correct course to return to earth. on april 17, apollo 13 landed safely in the pacific ocean.
what is the main, or central, idea of the passage?
after an explosion on apollo 13, the astronauts had to conserve supplies.
after an explosion on apollo 13, the spaceship began to lose air, water, and power.
after an explosion on apollo 13, the astronauts took shelter in the lunar module.

Explanation:

The passage details the Apollo 13 mission, starting with its launch for a moon landing. Then, an oxygen tank explosion occurs, leading to loss of air, electricity, and water. The moon landing is canceled. The astronauts move into the lunar module (which has fewer supplies, so they conserve food and water) and use its engine to get on the correct course back to Earth. Finally, Apollo 13 lands safely. The first option only focuses on conserving supplies. The second option just mentions the loss of air, water, and power. The third option only talks about taking shelter in the lunar module. But the overall story is about the sequence of events after the explosion that led to the safe return of the astronauts. None of the given options fully capture the central idea. However, if we assume there are no other options and we have to choose the best among these, none is perfect. But if forced, the first option is too narrow (only about conserving supplies which is part of the story), the second is also narrow (only about the loss), the third is narrow (only about taking shelter). But if we consider that the passage's main flow is the events after the explosion leading to the solution (using the lunar module's engine etc. to return), and among the given options, the first - "After an explosion on Apollo 13, the astronauts had to conserve supplies" - is part of the story but not the whole. But if we assume these are the only options, and we have to pick the one that is a key part (as the other two are even more details), the first option is the most relevant among them.

Answer:

After an explosion on Apollo 13, the astronauts had to conserve supplies.