Many volunteers are trying _______ reserves for animals in d

tyr to do,努力做某事
try doing 尝试做某事
此题,志愿者努力为濒危动物建立保护区,用try to do

Many animals are in danger, the reason is human activities.--- --- --- - --- many animals are in danger because of human beings

是
try to do something, 固定用法

Many volunteers are trying _______ reserves for animals in danger.
A. building B. build C. built D. to build
根据句意可知答案应是D. try to do sth.意为“尽力做某事”。