Which two storylines can be correctly categorized as science fiction?
a 5-year-old child tells his parents about his past life that he can remember clearly.
a narrator recounts the day his hometown suffered an alien invasion.
a mountaineer describes his ascent to the highest peak in the world.
a teacher takes her class to the past in a time machine to investigate their roots.

B, D.

Explanation:

The two storylines which can be categorized as science fiction are A narrator recounts the day his hometown suffered an alien invasion, and A teacher takes her class to the past in a time machine to investigate their roots. Science fiction storylines are varied. Among the most common storylines of them are alien invasions like in the H.G. Wells "War of the Worlds", and time travel with a machine or other vehicle that can travel through time like in "The Time Machine" by H.G. Wells.

what are the sentences?

- "a nonrestrictive clause functions as a modifier to a noun (that is an object, person or concept). these clauses can be described by the following three options: it is set off by comas, it contains a subject and a verbs and it adds nonessential information to the sentence.

for example, in "here is bill gates, who confounded microsoft software company" we can identify "who confounded microsoft software company" as a nonrestrictive clause modifying the noun bill gates. this clause can be describes as a nonrestrictive clause because it is separated by a comma, it adds nonessential information to identify who bill gates is and it must contain both a subject (who) and a verb (confounded)."