What should be added to one rational expression to get another

1. A.
   $\frac{1}{(x^2 - 7x + 12)}$
2. B.
   $\frac{1}{(x^2 + 7x + 12)}$
3. C.
   $\frac{1}{(x^2 - 7x - 12)}$
4. D.
   $\frac{1}{(x^2 + 7x - 12)}$

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1. A.
   $\frac{x^2 - 1}{(x + 2)(x^2 + 1)}$
2. B.
   $\frac{x^2 + 2}{(x + 2)(x^2 + 1)}$
3. C.
   $\frac{x + 1}{x + 2}$
4. D.
   $\frac{x - 1}{x + 2}$

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