You Are an Antique Hound

You are an antique hound. You buy an old xylophone and play it, making note that the bars on it act like harmonic oscillators when they are struck. You also see that the bars have become very dirty through years of use, so you thoroughly clean them. Removing the accumulation from the bars will

A) not affect their pitch or sound volume.
B) raise their pitch.
C) lower their pitch.
D) not affect their pitch, but will reduce their sound volume.