--- Lucy seems in low spirits.
--- Yes, all her efforts were and no one was interested in her invention.
A. in need
B. in vain
C. in place
D. in use
网友回答
A. in need
(答案→)B. in vain
C. in place
D. in use
解析：考查介词短语：句意：--露西好像情绪低落。--是，她的努力似乎是徒劳的，没有人对她的发明感兴趣。A. in need 需要，B. in vain徒劳，C. in place在适当的位置，D. in use在使用中，所以选B。