Final answer:
By cross-multiplying the equation x/y = u/v, we determine that the statement xv = yu must be true, which corresponds to option B.
Step-by-step explanation:
If we start with the equation x/y = u/v, we can cross-multiply to find a relationship between these variables.
Cross-multiplication gives us xv = yu.
Therefore, the correct statement that must be true is option B) xv = yu.
To further illustrate this, when we cross-multiply, we multiply x by v and y by u, resulting in the equation xv = yu.
No other options provided result in an equality when we apply cross-multiplication to the original equation x/y = u/v.