单项选择题

Almost everyone has a hobby. A hobby can be 21 people like to do in their spare time. A hobby can 22 them with interest, enjoyment, friendship, knowledge and 23 It can be something 24 they learn more about themselves or about the world. It may introduce them to friends who share their enthusiasm and from whom they can also learn. It helps both manual 25 mental workers relax after periods of hard work. It also offers interesting and enjoyable 26 for retirees. 27 , it can benefit people"s mental and physical health.
Different people have different hobbies. People who 28 ,hobbies are hobbyists. Some paint pictures, sing pop songs, 29 on musical instruments and enjoy 30 coins or stamps; others 31 flowers, go fishing, hunt animals or spend their time 32 sports: climbing mountains, swimming, skating and playing 33 Anyone, rich or poor, old or young, 34 or well, can follow a satisfying hobby, 35 his age, position, or income.
36 for me, I like sports very much. Sometimes I play tennis or badminton or go swimming. Sometimes I exercise 37 and go running regularly in the morning. 38 I choose, if I exercise regularly, I will be sure to 39 and improve my health 40 my life.

A.solely
B.merely
C.alone
D.lonely