which sentence or sentences have correct parallel structure? while thousands of people hike the inca trail…

which sentence or sentences have correct parallel structure? while thousands of people hike the inca trail to visit machu picchu, no one really knows if the incas built the ancient mountaintop complex as a ceremonial site, a royal estate, or to protect themselves from intruders. while thousands of people hike the inca trail to visit machu picchu, no one really knows if the incas built the ancient mountaintop complex as a ceremonial site, a royal estate, or a military fortress.

which sentence or sentences have correct parallel structure? while thousands of people hike the inca trail to visit machu picchu, no one really knows if the incas built the ancient mountaintop complex as a ceremonial site, a royal estate, or to protect themselves from intruders. while thousands of people hike the inca trail to visit machu picchu, no one really knows if the incas built the ancient mountaintop complex as a ceremonial site, a royal estate, or a military fortress.

Answer

Brief Explanations:

Parallel structure requires items in a list to have the same grammatical form. In the second - sentence, "a ceremonial site", "a royal estate", and "a military fortress" are all noun phrases, maintaining parallelism. In the first sentence, "a ceremonial site", "a royal estate" are noun phrases but "to protect themselves from intruders" is an infinitive phrase, breaking parallelism.

Answer:

The second sentence "While thousands of people hike the Inca trail to visit Machu Picchu, no one really knows if the Incas built the ancient mountaintop complex as a ceremonial site, a royal estate, or a military fortress." has correct parallel structure.