[单项选择]

13-15
A hobby can be almost anything a person likes to do in his spare time. Hobbyists raise pets, build model ships, or carve soap figures, They watch birds, hunt animals, climb mountains, raise flowers, fish, ski, skate, and swim. Hobbyists also paint paint pictures, attend concerts and plays, and perform on musical instruments. They collect everything from books to butterflies, and from shells to stamps.
People take up hobbies because these activities offer enjoyment, friendship, knowledge, and relaxation. Sometimes they even produce financial profit. Hobbies help people relax after periods of hard work, and provide a balance between work and play. Hobbies also offer interesting activities for persons who have retired. Anyone, rich or poor, old or young, sick or well, can follow a satisfying hobby, regardless of his age, position, or income.

At what time can a person have his hobby （）
A. In his spare time.
B. In his work time.
C. In his workday.
D. In his summer.