Fill in the Blank with One of the Words or Phrases

Fill in the blank with one of the words or phrases listed below. Not all choices will be used. $$\begin{array} { l l l l } \text { least common denominator } & \text { simplifying } & \text { reciprocals } & \text { numerator } \\\text { cross products } & \text { ratio } & \text { proportion } & \text { denominator } \\\text { rational expression } & \text { domain } & \text { complex fraction } & \\\frac { - a } { b } & \frac { a } { - b } & \frac { - a } { - b } &\end{array}$$
- $\frac { x } { 2 } = \frac { 7 } { 16 }$ is an example of $\mathrm { a } ( \mathrm { n } )$ _____

A) complex fraction
B) least common denominator
C) proportion
D) reciprocals