A、To work in mining operations. B、To carry scientific supplies. C、To cross the North American continent. D、To help cultivate the

I am glad that all the members of our zoology class could come down to the zoo today to continue our animal adaptation.  As you know, some animals are able to move between domestic and wild environments with relatively little difficulty. The first example of this that we will see here at the zoo is the wild burro. As you are probably aware, burros are relatives of the horse. Wild burros in the United States are descendants of the pack animals brought here three centuries ago by Spanish explorers, and these pack burros were in turn the descendants of wild African asses.
    About 100 years ago, gold prospectors came to the mountains and deserts of the western United States. Most of the prospectors were accompanied by steadfast companions—burros. These animals were used along with the mule train that served the many mining operations. But when gold and silver mining died out, many of the prospectors turned their burros loose, they joined wild burros that were already roaming the hills and canyons who were the descendants of those brought by the Spanish.  The prospectors knew that their burros were hardy animals, completely able to take care of themselves in the wild. The fact that there are over 11 thousand wild burros living in the western states today testifies to their great adaptive ability.