Answer is d using a heavier string
Silicon is a metalloid (:
We use a spectrometer to help us determine what stars and planets are made of by passing a light through various chemical elements, different spectral patterns are created. By matching those patterns up to patterns generated in a laboratory environment we can tell what the composition of a distant star or planet is.
In physical chemistry, the mean free path is the average distance between the atoms during collision. Its formula is

where d is the diameter of the Nitrogen atom (d = 310 x 10^-7 m), Na is Avogadro's number (Na=6.022 x 10^23), R is the gas constant (8.314 J/mol-K), T is the absolute temperature (T= 20 + 273 = 293 K). Substituting the values,
P = 6.32 x 10^-13 Pascals
A sound wave can not value in a vacuum, so its speed is 0.
Sound waves are longitudinal and require a medium to pass through.