You may easily lose your way in Shanghai ______ you don’t have a map or a guide.

I wonder if you _____ on a trip to Da lian.— If it _____ tomorrow, we will go. [ ]

In the United States, Father’s Day falls on ________ third Sunday in ________ June.

Look at ______ book on the desk . Is it ______ useful one ?–Yes, it is . In the book there is much advice on how to learn math well.

As a volunteer ,Guo Mingyi ______always _____help others who are in trouble .