1.The scientists are doing everything they can _____ the dying Northeast Tigers.
A. save B. to save C. saving D. to have saved
2. He came into the classroom through the back door_____ being seen by anyone.
A. in B. for C. to D. without
3. John plays football _____, if not better than, David.
A. as well B. so well C. as well as D. so well as
