Read the following sentence.

Although most flash mobs gather to make a statement some gather to protest something.

Which of the following identifies the type of sentence used in the example above and punctuates it correctly?
A. simple; It is punctuated correctly.
B. complex; Although most flash mobs gather to make a statement, some gather to protest something.
C. compound-complex; Although most flash mobs gather to make a statement, some gather to protest something.
D. compound; Although most flash mobs gather to make a statement; some gather to protest something.