In the reading room, we found her _____ at a desk, with her attention _____ on a book[ ]

Today the forests are getting fewer and fewer. We must _______ down too many trees.

How are you going, Buddy—-________. A little busy, though.

With the fast development of computer and Internet technologies, traditional printed books ______ by the growing popularity of online reading of e-books

What can trees do _________ us — They can _________ harmful gases and produceoxygen .