identify the prepositional pharse. vouluntary muscles, which help you move are joined to your bones. ) to your bones C)are joined to your bones d) are joined i think its c.

No. C is not correct.

A prepositional phrase begins with a preposition and ends with a noun or pronoun.

Check this list of prepositions to see which is the prepositional phrase.

http://www.englishclub.com/grammar/prepositions-list.htm

is it a.

I don't see "a" as a possible answer above.

The prepositional phrase in the sentence "Voluntary muscles, which help you move, are joined to your bones" is "to your bones."

To identify the prepositional phrase, you need to locate a preposition and its object. In this sentence, the preposition is "to" and its object is "your bones." The prepositional phrase functions as an adjective (providing more information about the verb "are joined") and answers the question "joined to what?".

Therefore, the correct answer is C) "to your bones."