Multiply $\frac{x^{2}-49}{y}$ and $\frac{12}{(x-7)^{2}}$. (A) $\frac{12(x+7)}{y(x-7)}$ (B) $\frac{12(x+7)}{y}$ (C) $\frac{12(x-7)}{y(x+7)}$ (D) $\frac{12(x-7)}{y}$

Step 1 ：The problem is asking us to multiply two fractions: \(\frac{x^{2}-49}{y}\) and \(\frac{12}{(x-7)^{2}}\).

Step 2 ：We can simplify the first fraction by factoring the numerator, \(x^{2}-49\), which is a difference of squares and can be factored into \((x-7)(x+7)\).

Step 3 ：Then we multiply the two fractions to get the result.

Step 4 ：The result of the multiplication of the two fractions is \(\frac{12(x+7)}{y(x-7)}\).

Step 5 ：Comparing this with the given options, it matches with option (A).

Step 6 ：Final Answer: \(\boxed{(A) \frac{12(x+7)}{y(x-7)}}\)