Express as the Logarithm of a Single Expression $\left( \log _ { a } x - \log _ { a } y \right) + 3 \log _ { a } z$

Multiple Choice

Express as the logarithm of a single expression. Assume that variables represent positive numbers.
- $\left( \log _ { a } x - \log _ { a } y \right) + 3 \log _ { a } z$

A) $\log _ { a } \frac { x } { z ^ { 3 } y }$
B) $\log _ { a } x z ^ { 3 } y$
C) $\log _ { a } \frac { 3 x z } { y }$
D) $\log _ { a } \frac { x z ^ { 3 } } { y }$