She said,"My dog died yesterday.（改为间接引语）
She said that her dog had died the day before.
她说她的狗之前一天已经死了.
宾语从句要改为过去完成时态,yesterday也要改.She said"This book may be helpful to you.改为间接引语She said that that book might be helpful to you.
她说那本书也许对你有用。