The correct answer is $\boxed{\text{B) 15 km/h}}$.
The formula for calculating the speed over the points while passing the signal is:
$$\text{Speed} = \frac{T}{369(I)}$$
where:
- $T$ is the time in seconds it takes to travel from the starting point to the signal,
- $I$ is the grade of the track in percent, and
- $369$ is a constant.
In this case, $T = 1$ second and $I = 1$ percent. Substituting these values into the formula, we get:
$$\text{Speed} = \frac{1}{369(1)} = \boxed{15 \text{ km/h}}$$
Option A is incorrect because it is the speed of the train after getting T/369(I) seconds. Option C is incorrect because it is the speed of the train after getting T/369(I) seconds and passing the signal. Option D is incorrect because it is the speed of the train after getting T/369(I) seconds and passing the signal on a level track.