—Where are the papers for the Smith project?—They are in the folder ________ “S”．

 Sustainable development is long-term ________which focuses on the environment and  ________ natural resources.

__________the teacher entering  the classroom, the boy pretended _______ the text.

The ______ boy was last seen ____ near the East Lake.     

________ your dog with me should be a good choice. Trust me and I’ll look after it well.