Which statement is an example of a theme?
a. sacrifices and hard work pay off in the end, despite the challenges along the way.
b. a working college student misses out on fun activities, but his hard work him appreciate his degree.
c. gene has to work nights to pay for college and is unable to attend all the cool parties.
d. gene's hard work pays off in the end, and he graduates from the university at the top of his class.

Sacrifices and hard work pay off in the end, despite challenges along the way.

Theme does not describe what a character did. Theme is what the character learned.

3rd person, because the narrator is out of the story but explains the feeling of the main character

faulty parallelism is a construction in which two or more parts of a sentence are equivalent in meaning but not grammatically similar in form.

the correct version of this faulty parallelism in the sentence is:

the hikers knew that the hike was six miles, that it usually required the entire day, and it would not be wise to start after 10: 00 a.m.

the problem is the last sentence, the first two have a basic subject+verb+object structure.

so, to give a proper balance to the structure, or better said, to give a parallel structure, we must write a basic s+v+o structure in all three sentences:

the hikers knew that the hike was six miles, that it usually required the entire day, and it would not be wise to start after 10: 00 a.m.