For what has the hot-air balloon been used? A. daily traveling B. exploring space C. weather experiments D. learning about geology

- "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)."

hm, switch the relative; nominative and indefinite; objective ? not too bright in the knowledge of the english.

they are all talking about chocolate (next time you post a question with "which" post the choices too)