1) The halftime performers whirled through a complex series of choreographed moves. 2) Twirling their batons so fast they resembled helicopter blades.
Which option explains why Section 2 is a sentence fragment?

a. It begins with participle verb form and therefore must be linked with what it modifies in an independent clause or main sentence.
b. It does not contain a noun.
c. It begins with a coordinating conjunction and therefore must be linked with an independent clause or main sentence.
d. It does not contain a verb.