She can try and explore other things to make workout less boring :)
I’m thinking D because it will stop the bleeding.
Avoid riding on roadways. If there is a sidewalk you could ride on nearby, use it. Drivers get a little nervous if they're sharing the roadway with a bicycle. Avoid riding too long without breaks, you can get tired out and unintentionally harm yourself or others. Drink lots of water on the way, and wear helmets at all times, no matter how stupid you think they make you look. :)
The speed of an exercise has a lot to do with the intensity of cardiovascular exercise.
The more the speed of an exercise is the greater intensity of the workout is and the more you sweat. However after a certain time you get fatigued and tired out.
For example, if you had planned to do an exercise for 30 minutes and you increase the speed of the exercise then probably you might not be able to complete the 30 mins as youll get fatigued before that time due to the high intensity.