Answer: OPTION D.
Step-by-step explanation:
It is important to remember that a variation is Combined when a variable depends on two or more other variables. Then, this will vary directly with some of these variables and inversely with the others.
In this case, you have the following expression:
[tex]f=\frac{kw_1w_2}{s}[/tex]
Assuming that "k" is the constant of variation, you can observe that [tex]f[/tex] varies jointly as [tex]w_1[/tex] and [tex]w_2[/tex] and inversely as [tex]s[/tex].
Therefore, the variation is: COMBIINED.
