If you happen to get lost in the wild, you’d better stay ______ you are and wait for help.
Paul doesn’t know _________ about his problems.
--Who _______ the Harry Potter series________ ? -- J.K.Rowling.
We know that about seventy percent _____ the earth _____ covered by water.
The question is _________ .
-- Must I return the book this week?-- No, you ______. You can _____ it for 20 days.