Find All Numbers for Which the Rational Expression Is Not $\frac{2 y-6}{y^{2}-49}$

Multiple Choice

Find all numbers for which the rational expression is not defined.
- $\frac{2 y-6}{y^{2}-49}$

A) $y=49$
B) $y=7$
C) $y=7$ and $y=-7$
D) $y=3$