danger----dangerous----endanger----in danger reserve----reservation(保留预订) [ˌrezəˈveiʃən] habit---habitat habitable [ˈhæbɪtəbəl] 适合居住的 habitation [ˌhæbɪˈteɪʃən]居住 extinct----extinction struggle to one’s feet 挣扎站起来 protect---protection----protective be worth doing= be worthy of being done/ to be done on the spot air raid 空袭