Ihave looked at every website for this question

all of the following are forms of electromagnetic energy except

red light
infrared light
b-flat chord
an x-ray wave

And xray uses electromagnetic energy as well as infrared light and red light which is used for tanning and stuff. But the b-flat chord is a note on a piano or guitar. so I'm assuming the answer is bflat chord.

Answer. av valves opens;