I think one thing you could do in order to measure your cardiovascular strength you can do a full sprint run. In order to help improve your fitness levels you can swim, jog/run, body weight exercises, and a balanced diet.
A.) staying free of disease (physical)
B.) reflecting about yourself (mental)
C.) getting 8-10 hours of sleep each night (physical)
D.) engaging in 30-60 minutes of physical activity every day (physical)
Since B is a mental activity...
The answer = B. reflecting about yourself
Good Luck!
Answer:
By keeping a safe distance and watching their speed.