Renee realized that no one else was going to volunteer to help the librarian. She volunteered. That afternoon, Renee stocked the shelves with all the misplaced books. She also got to help "cull" the shelves of old books that were no longer worth keeping or in too bad a condition to get checked out again. During all of her work, Renee talked with and got to know the librarian better. In the end, Renee felt like she had had a better afternoon working than any of her friends playing.
Which is the most effective combination of the first two sentences of this paragraph?

A) Renee realized that no one else was going to volunteer to help the librarian, so she volunteered.
B) Renee realized that no one else was going to volunteer to help the librarian, but she volunteered.
C) Renee realized that no one else was going to volunteer to help the librarian, and she volunteered.
D) Renee realized that no one else was going to volunteer to help the librarian, yet she volunteered.