Answer:
D Electromagnetic and gravitational
A beat is an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies. Frequency beat is equal to,

The reference frequency in our case would be 392Hz, and since there is the possibility of the upper and lower range for the amount of beats per second that the two possible frequencies are heard would be


Therefore the two possible frequencies the piano wire is vibrating at, would be 396Hz and 388Hz
C beautiful yellow silk
D was sleeping
<span>1. No energy is gained or lost when molecules collide.
2. The molecules in a gas take up a negligible (able to be ignored) amount of space in relation to the container they occupy.
3. The molecules are in constant, linear motion.</span>
The dye in between the two pieces of glass in the filter absorbs all the other colors in the white light except the red, and the red is the only light left to come out the other side. That's why the filter usually looks kind of red. It's also a big part of the reason why we call it a "red filter".