1. Wild plants and animals need food, a good environment and safety. If their habitat is threatened or they cannot find enough food, their numbers may ______ .

A. discourage                                                   B. decrease

C. disturb                                                               D. disgust

2. If we don’t take steps, some rare animals, such as the Tibetan antelopes and pandas£¬ will _____ some day just as dinosaurs.

A. die out                                                               B. die away

C. die down                                                     D. die off