单项选择题

Passage One Questions 26 to 29 are based on the conversation you have just heard.

Why do the 4-H girls agree to follow the park project through to complete.()

A.They were obliged to fulfill the signed contract.
B.They were encouraged by the city officials’ praise.
C.They wanted to prove they were as capable as boys.
D.They derived happiness from the constructive work.