1. a physical benefit would be you get more fit from activity. a mental/ emotional benefit would be you release endorphins and they make you happier. a social benefit would be (if you work out in groups or are on a team) you get social activity and make friends even!
2. agility, balance, coordination, speed, power, and reaction time.
3. Internal influences on physical activity:  Can you reach your Target Heart Rate just walking or do you have to jog/run? 
External: Money; how much can you spend on fitness?
4. Always wear sunscreen. 
Avoid sun in the middle of the day, from about 10 a.m. to 3 p.m. 
Wear protective clothing
Wear sunglasses that filter UV light.
<em>hope this helps :) </em>