The correct answer is A. 0.00018 m3/sec.
The discharge per meter length of dam can be calculated using the following equation:
$Q = K\frac{i^2}{n}$
where:
- $Q$ is the discharge per meter length of dam (m3/sec)
- $K$ is the coefficient of permeability of dam material (mm/sec)
- $i$ is the hydraulic gradient (-)
- $n$ is the number of flow channels
In this case, we know that $K = 0.03$ mm/sec, $i = \frac{30}{25} = 1.2$, and $n = 5$. Substituting these values into the equation, we get:
$Q = 0.03 \cdot \frac{1.2^2}{5} = 0.00018$ m3/sec
Therefore, the discharge per meter length of dam is 0.00018 m3/sec.
Option B is incorrect because it is the discharge per meter length of dam for a different set of conditions. Option C is incorrect because it is the discharge per meter length of dam for a dam with a different water depth. Option D is incorrect because it is the discharge per meter length of dam for a dam with a different coefficient of permeability.