I think c would be the answer
Either let them know you are there or check your blind spots
Okay, this is an interesting one but mainly no, most activity's will so you don't push yourself but if you really wanted to you could go for however long you want as long as you are not doing harm to your body, depending if you are on a fitness program there will be limits.
A sheriff. A sheriff is elected into office by the people of a certain district.
Hope this helps! (:
