Điền từ thích hợp: which we cut bread is very sharp

1. The knife........... which we cut bread is very sharp
A. whith that           B.which                  C.with which                       D.that
2. The authority gathered those villagers........... they explained the importance of forests
A. who                    B.to whom              C. whom                            D.to that
3. The little girl............. i borrowed this pen has gone.
A. whose                B. from who            C. from that                        D. from whom
4. Steve Irwin, to ............. we has to be grateful, spent all his life on promoting people's love to nature
A. whose                B. who                    C. that                                 D. whom