"Open here I flung the shutter, when, with many a flirt and flutter" sounds anything but formal. You might say that there's nothing scary about it either. The words have a sense of rhythm that prevents those lines to feel slow. The correct answer, considering how the author phrases the lines and uses "flirt and flutter" and "stately Raven of the Saintly Days", the correct answer is most likely:
C.Playful
