The correct answer is: 100%.
CC rake goods trains are required to have 100% brake power at the starting station. This is to ensure that the train can be stopped safely in the event of an emergency. The brake power is provided by a system of air brakes, which are activated by the driver. The air brakes work by applying pressure to the brake shoes, which then rub against the wheels to slow the train down.
The brake power of a train is measured in percent. The higher the percent, the more powerful the brakes. A train with 100% brake power has the maximum amount of braking power available. This is important for CC rake goods trains, as they are often very heavy and can be difficult to stop.
If a CC rake goods train does not have 100% brake power at the starting station, it could be dangerous. In the event of an emergency, the train may not be able to stop in time, which could lead to a collision. Therefore, it is important to ensure that all CC rake goods trains have 100% brake power at the starting station.
The other options are incorrect because they do not represent the required brake power for CC rake goods trains. Option A, 75%, is too low. Option B, 50%, is even lower. Option C, 90%, is closer to the required brake power, but it is still not enough. Option D, 100%, is the correct answer.