Write as a Logarithm of a Single Expression $3 \log _ { 5 } 3 + \frac { 1 } { 7 } \log _ { 5 } ( r - 7 ) - \frac { 1 } { 2 } \log _ { 5 } r$

Multiple Choice

Write as a logarithm of a single expression.
- $3 \log _ { 5 } 3 + \frac { 1 } { 7 } \log _ { 5 } ( r - 7 ) - \frac { 1 } { 2 } \log _ { 5 } r$

A) $\log _5 \frac { 27 \sqrt [ 7 ] { r - 7 } } { \sqrt { r } }$
B) $\log _5 \left( \frac { 3 } { 14 } \sqrt { \frac { r - 7 } { r } } \right)$
C) $\log _ { 5 } \sqrt { \frac { 3 r - 21 } { 14 r } }$
D) $\log _5 \frac { 27 r - 7 } { 14 r }$