题干
The flood is believed ____ more than 50 people and made thousands homeless, ____ it perhaps the most destroying flood in history in the area.
A：killing; to make
B：to have killed; making
C：to have killed; having made
D：having killed; making
答案(点此获取答案解析）
B
，当
时，
，且满足下列条件:
②
, ③
．则
等于