As a volunteer of the 2012 London Olympic Games, which sign will you prepare to remind people to keep the environment clean?
----Which is _______ to understand, this book or that book? ---- I think both of them are quite easy.
----______ is the lady in white? ----She is a nurse.
----Do you know _______ young man under the tree? ----Yes, but only a little, maybe he is _______ university student.
My father goes for a walk daily.
The little girl is fortunate to get help from so many strangers.