25. Given the current pollution problem, people are seriously considering settling ______ a new land like Mars to start life fresh.

   A. of                          B. on                         C. under                        D. off

26. Doctors consider ______ of great importance that pregnant women should be more careful than ordinary people in the explosion of H1N1 virus.

   A. that                       B. which                    C. it                              D. this