A professor of biology gave a talk to more than 1000 students on elephants living conditions and the dangers them.
A. face
B. facing
C. faced
D. are facing
网友回答
A. face
(答案→)B. facing
C. faced
D. are facing
解析：考查非谓语动词。facing them作定语，修饰living conditions and the dangers，故选B。