【题目】In spite of all the efforts __________ these endangered species, many of them have died out over the years.
A. to protect B. protecting
C. protected D. having protected
在线课程【答案】A
【解析】句意：尽管为保护这些濒危物种做出了努力，但是，多年来仍有许多物种灭绝了。efforts to do sth. 为做某事而做出努力，不定式作定语。