We collected a lot of books to get the necessary information but only half _________helpful, so we failed to finish the work. 

 You, who ______ his good friend, should help him get out of trouble. 

One or two days ____quite enough to complete the work. ___ you or he going to work with me?

He always dreams of ______ a chance for him to go abroad for further study．

When  ______  the United Nations founded?