The right answer is
2) NaCl
In fact, from the definition of acid, all acids contain at least one atom of hydrogen. In the options given by the problem, all compounds contain at least one atom of hydrogen H, except for the NaCl: therefore, NaCl is not an acid.
The longer or denser the pasta or marshmallow, the lower the natural frequency. The stiffer the pasta, the higher the natural frequency. Depending on these factors, each type of pasta will have its own natural frequency. The short piece of pasta will have a different natural frequency than the long piece of pasta.
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The distance from the sun to Neptune is about the same as the distance from Neptune to the next closest star, Proxima Centauri
Use a sped o meter enjoy!