30. \( a_{55:\overline{10}|} = ? \)(A) \( \frac{N_{55} - N_{65}}{D_{55}} \)(B) \( \frac{N_{55} - N_{65}}{D_{65}} \)(C) \( \frac{N_{56} - N_{66}}{D_{55}} \)(D) \( \frac{N_{56} - N_{66}}{D_{56}} \)