D. Model number 2
Hope this helps!! (:
Explanation:
The first wave was found to have a wavelength of 3 x 10⁵ m and the second wave had a wavelength of 3 x 10⁴ m
We need to find which wave have a higher frequency.
The relation between frequency and wavelength is given by :

Let f₁ and f₂ be the frequency of wave 1 and wave 2.

And

Hence, the wave having less wavelength will have higher frequency. The wave having wavelength 3 x 10⁴ m will have higher frequency.
3. Atoms change into other atoms in chemical reactions.
The idea that you can transform one element into another was called alchemy, and was proven untrue a long time ago.
<span>Not all solids melt when they are heated. Some may undergo chemical changes as a result of heating. For example paper burns rather than melts</span>