The mechanical advantage (MA) of a lever can be calculated using the formula:
\[ \text{Mechanical Advantage} (MA) = \frac{\text{Effort Arm Length}}{\text{Load Arm Length}} \]
In this case, the effort arm length is 15 meters and the load arm length is 5 meters. Plugging in the values:
\[ MA = \frac{15 , \text{meters}}{5 , \text{meters}} = 3 \]
Therefore, the mechanical advantage is 3.
So, the correct response is 3.