根据短文内容，从短文后选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
Physical activity is known to reduce the risk of some diseases such as heart disease, stroke and diabetes. It is also known to increase the release of endorphins(安多芬)which reduce feelings of pain and help people feel more happy and peaceful.
  Some experts believe it is the act of exercising itself. Others say it is the feeling one gets from having met an exercise goal. Either way, the two things work together when it comes to improving one’s emotional health.
 Aerobic exercise gets out heart rate going faster and increases our breathing. Activities like walking at an increased speed, dancing, swimming or riding a bicycle are good examples. Muscle-strengthening activities help build and strengthen muscle groups in the body.   
Experts sat adults should get at least two and a half hours of aerobic exercise each week. Mote intense activities reduce the suggested amount of time to one hour and fifteen minutes.    
Earlier advice from the Centers for Disease Control said people need to exercise thirty minutes each day for at least five days to get the health benefits of exercise. More recent research suggested that those gains are the same whether you exercise for short periods over five days or longer sessions over two or three days.   They help people guarantee that they stay with the program.

A．There are two separate , but equally important kinds of physical activity.

B．This kind of exercise includes lifting weights, or doing sit-ups and push-ups.

C．Health experts have long noted the importance of physical activity.

D．There is some debate about exactly what causes the brain to release endorphins.

E．Experts say people should choose physical activities that they find fun.
F．Some examples are playing basketball, swimming and distance running.
G．Physical activity can help people reduce the risk of getting diabetes.