B.Brother and sister.
C.Schoolmates.
听第10段材料,回答第17至20题。
17.How often does the competition take place?
A.Every year.
B.Every other year.
C.Every four years.
18.How many people took part in the competition this year?
A.At least 100.
B.At least 120.
C.At least 200.
19.Who is the competition intended for?
A.Young songwriters.