Вкаких случаях пишется is а когда are .

sport has always played an important role in our life.

exercise means going in for sports but choosing those sports which suit you.

many people jog, walk or cycle in their free time/ physical exercises help you keep fit, have a good gait and figure. they also help you lose weight and work out energy. it is believed that professional sport keeps people fit and healthy. sportsmen have gook figures and strong muscles. they are usually attractive. they develop positive traits of character and learn how to work hard, to be strong, patient, well-organized and disciplined. but few piople remember about disadvantages of hoing in for sports. sport takes much time, people do not like to lose. when they lose, they feel uneasy and unhappy. the third disadvantage which i should mention is risk. going in for sports can cause many injuries.